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Abstract:

The invention provides methods of making laminated devices (especially
microchannel devices) in which plates are assembled and welded together.
Unlike conventional microchannel devices, the inventive laminated devices
can be made without brazing or diffusion bonding; thus providing
significant advantages for manufacturing. Features such as expansion
joints and external welded supports are also described. Laminated devices
and methods of conducting unit operations in laminated devices are also
described.

Claims:

1. A laminated microchannel assembly comprising a first sheet and a
second sheet; wherein each sheet has a length and a width, wherein the
cross section defined by the sheet length multiplied by the sheet width
is greater than 100 cm2; wherein the first and second sheets are
substantially flat; wherein the first sheet comprises an array of
parallel microchannels, wherein the microchannels are separated from each
other by a barrier wall; wherein the first sheet and the second sheet are
adjacent; and comprising welds that run along the length of the barrier
walls and join the first sheet to the second sheet.

2. The microchannel assembly of claim 1 wherein the cross section defined
by the sheet length multiplied by the sheet width is greater than 500
cm2.

3. The microchannel assembly of claim 1 wherein the welds are continuous.

4. The microchannel assembly of claim 1 wherein the welds on the second
sheet have a linear density of at least 2.7 cm/cm.sup.2.

5. The microchannel assembly of claim 1 wherein the welds are laser welds
having a width of 0.015 cm or greater.

6. A method of making a laminated device, comprising: providing a first
subassembly or a first sheet and a second subassembly or a second sheet;
wherein the first subassembly or first sheet comprises a first parallel
array of channels and wherein the second subassembly or second sheet
comprises a second parallel array of channels and wherein there is no
intersection between channels in the first subassembly or first sheet and
the second subassembly or second sheet; welding an edge of the first
assembly to an edge of the second assembly to form a combined subassembly
layer of welding edges of the first and second sheets to form a welded
single sheet; and stacking the combined layer or welded single sheet with
one or more layers or sheets, and joining the stacked layers or sheets to
form a laminated device.

7. The method of claim 6 wherein the first and second arrays of parallel
channels can share a common header or footer.

8. The method of claim 6 wherein the first assembly is welded to the
second assembly by spot welding.

9. The method of claim 6 wherein a single sheet or subassembly is cut
into plural pieces and subsequently welded together to form an assembly.

10. The method of claim 6 wherein the first subassembly or first sheet is
the same size as the second assembly or second sheet.

11. The method of claim 6 further comprising a step of flattening the
first subassembly or first sheet prior to welding the edges together.

12. A laminated device made by the method of claim 6.

13. A method of conducting a process in a channel layer that changes from
tension to compression or vice versa, comprising providing a device
comprising a first channel layer, and a second channel layer directly
adjacent to the first channel; wherein, at a first time, the first
channel layer comprises a first fluid at a first pressure and the second
channel layer comprises a second fluid at a second pressure; wherein the
first pressure is greater than the second pressure; conducting a unit
operation in the first channel layer at the first time; wherein, at a
second time, the first channel layer comprises a third fluid at a third
pressure and the second channel layer comprises a fourth fluid at a
fourth pressure; wherein the fourth pressure is greater than the third
pressure; conducting a unit operation in the first channel layer at the
second time.

14. The method of claim 13 wherein the first and third fluids are be a
Fischer-Tropsch process stream and the second and fourth fluids are a
heat exchange fluid.

15. The method of claim 13 conducted in a welded, laminated device
wherein the first channel comprises a thermally conductive a press-fit
insert and a catalyst.

16. The method of claim 13 wherein, as solids build up in the first
channel, process conditions are adjusted to accommodate changes within
the reactor.

17. A laminated microchannel device having a length and a width, wherein
the cross section defined by the sheet length multiplied by the sheet
width is greater than 100 cm2 and, is joined with a top plate to form a
welded assembly with a linear density of laser welded joint of between
0.05 to 20 cm/cm2 over a section of a surface of a sheet within the
microchannel device; this section comprises at least 50% (preferably at
least 90%, in some embodiments 100%) of contiguous area of a major
surface.

18. The laminated microchannel device of claim 17 wherein the cross
section defined by the sheet length multiplied by the sheet width is
greater than 500 cm2 and, is joined with a top plate to form a welded
assembly with a linear density of laser welded joint of between 0.05 to
20 cm/cm2 over a section of a surface of a sheet within the microchannel
device; wherein this section comprises 100% of a major surface.

19. A method of forming a laminated assembly, comprising: welding a top
sheet to a bottom sheet to form a plurality of channels disposed between
a top surface of the top sheet and a bottom surface of the bottom sheet;
wherein welding is used to form seals between the channels in the
plurality of channels.

20. The method of claim 19 wherein the method of joining sheets into
assemblies comprises laser welding to seal between two adjacent interior
flow microchannels.

21. A laminated device comprising: a stack of sheets joined by welding;
the stack of sheets comprising a core stack of sheets joined by welding
along the perimeter of the sheets; and a strain relief joint within the
stack of sheets; wherein the strain relief joint comprises two adjacent
sheets that are held within the stack but are substantially not joined to
each other along the perimeter of two adjacent sheets.

Description:

[0002] The conventional thinking in microchannel technology is that
optimal heat transfer in a microchannel heat exchanger can only be
obtained by diffusion bonding and/or brazing. These methods rely on the
formation of a contiguous metallic interfaces between the layers. The
contiguous interface eliminates a thermal contact resistance between
layers and is believed to be necessary for moving high levels of heat
from an exothermic reaction to heat removal chambers or to add heat to an
endothermic reaction.

[0003] Brazing requires the addition of an interlayer material which melts
at a temperature below the melting temperature of the materials of
construction. The interlayer becomes liquid during the diffusion brazing
or brazing process. The liquid interlayer flows to fill gaps or voids
such that the materials are joined together. As the interlayer flows it
also experiences diffusion, where materials from the interlayer may
diffuse into the parent material and material from parent may diffuse
into the interlayer. As the diffusion progresses the local composition of
the interlayer material changes. Further, as the temperature is dropped
after achieving a maximum temperature, the liquid interlayer will
solidify and fill the voids between the two parent layers. Solidification
may be driven by temperature or composition. In the latter case a melting
point depressant, such as phosphorous or boron, is added to cause the
composite interlayer to melt at a lower temperature than the parent
material. In an analogous example, a diffusion bonded device also forms
intimate thermal contact between heat transfer layers.

SUMMARY OF THE INVENTION

[0004] In one aspect, the invention provides a method of making a
laminated device, comprising:

providing a bottom sheet, a top sheet and wherein there is a gap disposed
between a surface of the top sheet and a surface of the bottom sheet
[note that the top and bottom sheets can be part of subassemblies];
providing a thermally conductive fin insert having a height that is at
least 1% greater (preferably at least 2% greater, and in some embodiments
1 to 10% greater) than the gap height, placing the fin insert in the gap;
and pressing the sheets together such that the fin insert deforms to fit
within the gap.

[0005] The insert may or may not have a catalyst coating. In some
preferred embodiments, the resulting device has an irregular
configuration in which the insert is deformed in an irregular fashion,
for example, the crushed walls do not all bow in the same direction, nor
in alternating directions. In some embodiments, the fins are primarily
(greater than 50%, preferably greater than 80%) bowed in the same
direction. The compressed fins do not have a regular shape such as is
present in a corrugated sheet.

[0006] In some preferred embodiments, a surface of the bottom and/or top
sheet has weld lines protruding from the surface; in some preferred
embodiments, the sheet comprises one or more internal weld lines with a
continuous length of at least 50% (preferably at least 80%) of the
sheet's length or width; and at least one side of the fin insert rests at
least partially (preferably fully) on the one or more weld lines.
Preferably, the direction of flow through the insert is perpendicular to
the weld lines. Surprisingly, we discovered that good thermal transport
was obtained in the presence of these weld lines, even where the weld
lines were interposed between a reaction chamber (i.e., the chamber
containing the press-fit plus catalyst) and a heat exchanger. In some
embodiments the fin insert is tack welded to the top or bottom surface,
in a more preferred embodiment, the fin insert is held in place by press
fit and is not joined to either surface by welding. Preferably, the fin
is disposed within a microchannel, and/or an adjacent heat exchanger
comprises microchannels.

[0007] As is the case with all the methods described herein, the invention
also includes a device formed by the method. The invention also includes
operation of the device formed by the method for conducting one or more
unit operations. Preferably, the devices mentioned herein are chemical
processors that are adapted for conducting one or more unit operations.

[0008] In another aspect, the invention provides a laminated device,
comprising:

a device comprising a fluid inlet connected to a process chamber and a
fluid outlet connected to the process chamber; wherein the process
chamber comprises a gap and a thermally conductive fin insert that is
disposed within the gap and touches the top and bottom of the gap;
further wherein the fin insert has an irregular shape that is caused by
an at least 1% compression of the fin insert within the gap; and a heat
exchanger in thermal contact with the process chamber. In this device,
the irregular shape is caused by compression of sheets on either side of
the gap such that the height of the fin insert is deformed by at least 1%
of fin height (where height is in the same direction as stack height),
preferably at least 2% and in some embodiments at least 5% and in some
embodiments in the range of 1 to 10%.

[0009] This device may contain any of the features mentioned herein. For
example, in some preferred embodiments, the insert does not have a
catalyst coating; in some preferred embodiments, catalyst particles are
present in the gap. A conductive fin insert is a fin that moves the heat
from the process occurring within the fin section to the adjacent heat
exchange layers. The fin insert is preferably made from a material with a
higher thermal conductivity than the material of construction of the heat
transfer layer. In some preferred embodiments, the conductive fin insert
has a thermal conductivity that is greater than 10 times and more
preferably greater than 100 times the effective thermal conductivity of
the catalyst disposed within the conductive fin structure. For most
materials, thermal conductivity is known and, if not, can be measured
using a standard ASTM method.

[0010] In a further aspect, the invention provides a method of conducting
a chemical reaction, comprising: passing at least one reactant into the
process chamber of the device of claim 2; conducting a process within the
process chamber, and, simultaneously, exchanging heat between the process
chamber and the heat exchanger.

[0011] In another aspect, the invention provides a method of making a
laminated device, comprising: providing a first subassembly or a first
sheet and a second subassembly or a second sheet; wherein the first
subassembly or first sheet comprises a first parallel array of channels
and wherein the second subassembly or second sheet comprises a second
parallel array of channels and wherein there is no intersection between
channels in the first subassembly or first sheet and the second
subassembly or second sheet; welding an edge of the first assembly to an
edge of the second assembly to form a combined subassembly layer or
welding edges of the first and second sheets to form a welded single
sheet; and stacking the combined layer or welded single sheet with one or
more layers or sheets, and joining the stacked layers or sheets to form a
laminated device.

[0012] Although there is no interchannel mixing of channels in the first
and second sheets, the first and second arrays of parallel channels can
share a common header and/or footer. In one example of this method, a
sheet (or a subassembly comprising plural sheets) is cut into four pieces
and the four pieces are welded back together along their edges--this is a
counterintuitive process since we are cutting a sheet and rejoining it
along edges that were previously cut. Nonetheless, this process has been
found to significantly reduce warpage and thus result in a superior
laminated article. In some broader aspects of this method, the first and
second sheets (or subassemblies) are not cut from a common piece, but
rather can be separately obtained. Preferably, the stacked layers are of
equal width and length (in some embodiments within 5% of length and
width; in some embodiments within 1% of length and width). The cuts (and
rejoining welds) should be parallel to channel length; in this
orientation, there is no risk to form blocked or discontinuous channels.

[0013] In some preferred embodiments, the aspect ratio of the first
subassembly in width:height and length:height is greater than 2, more
preferably greater than 10. In some preferred embodiments, the aspect
ratio of the first sheet or first subassembly in width:length or
length:width is 1.5 or more, more preferably 2 or more, in some
embodiments 4 or more. Height refers to stacking height, with width and
length being mutually perpendicular and length being in the direction of
fluid flow along the sheet. Preferably, the first subassembly or a first
sheet comprises at least 5 first parallel channels (preferably
microchannels); and the second subassembly or a second sheet comprises at
least 5 second parallel channels (preferably microchannels), and the
first and second subassemblies or sheets are joined along an edge to
result in a sheet or subassembly in with the first parallel channels are
parallel to the second parallel channels; and, preferably, a single
manifold serves both the first and second parallel channels. Preferably,
the first and second subassemblies or sheets are joined such that
adjacent parallel channels in the first and second assemblies or sheets
are within 2 cm, more preferably within 1 cm. in the width direction
(length is parallel to the net direction of flow through the device). The
resulting device will contain sheets that have welding seems that connect
segments of the sheet. In some preferred embodiments, especially those in
which the aspect ratio of the first sheet or first subassembly in
width:height or length:height is greater than 1, a step of flattening one
or more (and preferably all of) the subassemblies is conducted prior to
welding the edges together.

[0014] As with all the methods described herein, the invention includes
the article that results from this method.

[0015] The invention includes a laminated device comprising: a first layer
having dimensions of length and width; wherein the first layer comprises
a first section comprising a first plurality of parallel channels, and a
second section comprising a second plurality of parallel channels,
wherein the first and second pluralities of channels are parallel;
wherein the first and second sections are joined together by a joint and
wherein the joint is parallel to the parallel channels; and a second
layer, wherein the second layer is welded onto the first layer. In some
preferred embodiments, the first layer is a subassembly and the second
layer is a subassembly, and the layers are joined by a weld along the
perimeter of the layers. In a further aspect, the invention provides a
method of precambering to make a flatter subassembly. This method of
making a laminated device, comprises providing a metal sheet; deforming
the metal sheet; and bonding the deformed metal sheet into a laminated
device.

[0016] In a preferred embodiment, the metal sheet is deformed in an arc
with a curvature of at least 10 degrees from flat, in some embodiments a
curvature in the range of 10 to 80 degrees from flat. Parts are
preferably precambered from a flat state to build in deformation such
that when the stress of welding (especially laser welding) is added to
the parts, they return to a near flat state. The arc of curvature from a
flat state is less than 90 degrees, and preferably between 10 and 80
degrees. A more preferred range is from 30 to 70 degrees. In some
preferred embodiments, the metal sheet is stainless steel.

[0017] In another aspect, the invention provides a method of making a
laminated device, comprising: providing a subassembly; flattening the
subassembly; welding the subassembly to a sheet or second subassembly.
Preferably, the subassemblies are welded along their perimeters except
where there are openings for inlets or outlets. In some preferred
embodiments, this method is combined with any of the methods described
herein.

[0018] In another aspect, the invention provides a method of conducting a
process in a channel layer that changes from tension to compression or
vice versa, comprising providing a device comprising a first channel
layer, and a second channel layer directly adjacent to the first channel;
wherein, at a first time, the first channel layer comprises a first fluid
at a first pressure and the second channel layer comprises a second fluid
at a second pressure; wherein the first pressure is greater than the
second pressure; conducting a unit operation in the first channel layer
at the first time; wherein, at a second time, the first channel layer
comprises a third fluid at a third pressure and the second channel layer
comprises a fourth fluid at a fourth pressure; wherein the fourth
pressure is greater than the third pressure; conducting a unit operation
in the first channel layer at the second time.

[0019] In tension, pressure in the first channel layer is greater than in
the second channel layer and in compression, pressure in the first
channel layer is less than in the second channel layer. In the height
direction, a layer is defined by a floor and a roof and the tension or
compressive force is exerted on the floor or roof of the layer. In some
preferred embodiments, the first and third fluids are the same and the
second and fourth fluids are the same; for example, the first and third
fluids may be a Fischer-Tropsch ("FT") process stream and the second and
fourth fluids are a heat exchange fluid, typically water (or other heat
exchange fluid) that is undergoing partial boiling. Examples of other
processes may include syntheses of ethylene oxide, propylene oxide,
methanol, ammonia, styrene and hydrogenations and hydrotreating.
Preferably, the method is conducted in a laminated device with the first
channel disposed in a first layer and the second channel disposed in an
adjacent layer. More preferably, the process is conducted within a
laminated device comprising numerous (such as at least 10) alternating
layers of first and second channels. In some preferred embodiments, the
first channel comprises a press-fit insert, and in some preferred
embodiments the first channel comprises a catalyst, which is preferably
used in conjunction with the press-fit insert. We surprisingly discovered
that a device made without diffusion bonding or brazing (such as a press
fit device) can operate successfully under these conditions. Preferably,
this method is defined as occurring during continuous operation, rather
than occurring during shut down or start up. The process may occur, for
example, as solids build up in a process channel, and/or as catalyst
loses activity and process conditions are adjusted to accommodate changes
within the reactor.

[0020] In a further aspect, the invention provides devices in which a halo
(described below) connects sections of a device. Thus, the invention
provides a device comprising a first laminated assembly comprising a
plurality of stacked sheets; wherein a first side of the first laminated
assembly comprises a plurality of inlets or outlets; wherein an enclosure
is joined to the first side and extends out from the first side, and
encloses the plurality of inlets and outlets. Typically, the enclosure is
metal and is welded onto the first side of the first laminated assembly.

[0021] In some preferred embodiments, the device includes a second
laminated assembly comprising a plurality of stacked sheets; wherein a
first side of the second laminated assembly comprises a second plurality
of inlets or outlets; and wherein the enclosure connects the first
plurality of inlets or outlets to the second plurality of inlets or
outlets.

[0022] In another aspect, a laminated microchannel device having a length
and a width, wherein the cross section defined by the sheet length
multiplied by the sheet width is greater than 100 cm2 (in some
embodiments greater than 500 cm2) and, is joined with a top plate to
form a welded assembly with a linear density of laser welded joint of
between 0.05 to 20 cm/cm2 (preferably 0.1 to 10 cm/cm2) over a
section of a surface of a sheet within the microchannel device; this
section comprises at least 50% (preferably at least 90%, in some
embodiments 100%) of contiguous area of a major surface (sheets have two
major surfaces). In most cases, the sheet forms a surface of a
subassembly within a larger device. The welds hold together two or more
sheets. The welds may also provide for sealing between two adjacent
interior flow channels. In this device, "100% of contiguous area" means
the entire surface (not just 100% of a selected rectangular area;
likewise 50% and 90% means 50% and 90% of the entire surface. Preferably,
the sheet length to width ratio is greater than 2. In addition to, or as
an alternative to the stated linear density, the inventive device can be
defined as having internal welding (i.e., welds on the interior of a
sheet rather than the perimeter) that is at least 10 times greater,
preferably at least 100 times greater, than the circumference (perimeter)
of the device.

[0023] In another aspect, the invention provides a laminated microchannel
assembly comprising a first sheet and a second sheet; wherein each sheet
has a length and a width, wherein the cross section defined by the sheet
length multiplied by the sheet width is greater than 100 cm2 (in some
embodiments greater than 500 cm2); wherein the first and second sheets
are substantially flat (the sheets may have some warpage, but the sheets
are not corrugated); wherein the first sheet comprises an array of
parallel microchannels, wherein the microchannels are separated from each
other by a barrier wall (the microchannels may be partially through the
thickness of the first sheet (e.g. etched channels) or may be through the
entire thickness of the first sheet); wherein the first sheet and the
second sheet are adjacent; and comprising welds that run along the length
of the barrier walls (the welds can be continuous or discontinuous) and
join the first sheet to the second sheet.

[0024] The phrase "run along" means that the welds run in the same
direction as the barrier walls and contacts the barrier walls.

[0025] In any of the methods describes herein, an assembly can be formed
by joining two or more welded subassemblies, wherein the method of
welding two or more subassemblies to form an assembly may be the same
welding method or a different welding method. In some embodiments, welded
subassemblies can also contain joints formed by techniques other than
welding.

[0026] In a further aspect, the invention provides a method of forming an
assembly comprising welding a top sheet to a bottom sheet to form a
plurality of channels disposed between a top surface of the top sheet and
a bottom surface of the bottom sheet wherein welding is used to form
seals between the channels in the plurality of channels. The top and
bottom surfaces are the top and bottom surfaces of the laminated
assembly. For example, the bottom sheet could contain etched channels and
the top sheet could be a non-etched flat sheet. Preferably, the method of
joining sheets into assemblies comprises laser welding to seal between
two adjacent interior flow channels. In any of the embodiments described
herein, channels may preferably be microchannels.

[0027] In another aspect, the invention provides a welded substrate
assembly that has been undergone a repair process for sealing leaks or
holes in the primary welding step, wherein the repair process may
comprise the same weld methodology as the primary welding (typically
laser welding) or may utilize a secondary process such as TIG welding,
pulsed laser, CMT or other to reduce the number of leak points in a
welded substrate assembly.

[0028] In a further aspect the invention provides a welded substrate
assembly that may hold a differential pressure of more than 100 psig at
ambient temperature (more preferably more than 500 psig, and still more
preferably more than 800 psig at ambient temperature). The welded
assembly is a laminated device in which, during operation, flow of fluids
is primarily perpendicular to sheet thickness. In the welded assembly,
the seals for maintaining the differential pressure are not diffusion
bonded or brazed.

[0029] In another aspect, the invention provides a method of forming a
laminated, welded device comprising: obtaining a welded substrate
assembly that has a curvature of greater than 1 cm when sitting on a
level table; subjecting the welded substrate assembly to a flattening
process to create a substantially flat part with no more than 1 cm rise
above flat when sitting on a level table; and welding the flattened
substrate assembly to a subassembly to form the laminated, welded device.

[0030] In a further aspect, the invention provides a welded substrate
assembly comprising a plurality of channels that are sealed by welding
(the sealing is not the result of polymeric gaskets, brazing, diffusion
bonding, or other conventional techniques) and having a leak rate less
than about 0.5 psig per 15 minutes; or a leak rate less than 10 sccm
nitrogen (preferably less than 1 sccm nitrogen) when pressurized in
nitrogen at 100 psig and ambient temperature.

[0031] In a further aspect, the invention provides a pressure-resistant
laminated device comprising: a stack of sheets that are joined together
(preferably by welding); wherein the stack of sheets comprise a plurality
of channels within the stack, and at least one inlet and one outlet
connected to the plurality of channels; a continuous unattached span that
constitutes a void within the stack of sheets; first and second endplates
on opposing sides of the laminated device; and further comprising an
array of stiffening members which are held (for example, via welding) in
intimate contact with the major exterior faces of the endplates, and
extending continuously across a region aligned with the continuous
unattached span. The stiffness of the members of the array is such that
they resist bending in the stacking direction (i.e. the direction
orthogonal to the plane of the laminae). Preferably, the system further
comprises a process stream comprising hydrogen and/or a hydrocarbon
passing through the plurality of channels.

[0032] The invention also provides for the repair of welded devices. The
devices can be refurbished by removing one or more welds. By removing a
plate at one end of channels, selected channels can be plugged--thus
reducing hot spots or otherwise avoiding channels that have developed
defects. Alternatively, a device can be opened up by removing a perimeter
weld, and then subassemblies may be removed or replaced. In some
embodiments, a subassembly can be removed and refurbished prior to being
reinserted into a device. After removing and/or replacing a subassembly,
welding can again be used to close the device. To assist in disassembly,
one or more surfaces of a subassembly can be coated with a release layer
such as a coating of zirconia or yttria, or insertion of grafoil or
ceramic paper between subassemblies.

[0033] The invention also includes methods of maintaining a reactor by
opening a weld and removing or replacing: catalyst (such as particulate
catalyst), a fin or waveform, or a subassembly. The device may then be
welded back together. The invention further includes devices having weld
structures resulting from the maintenance or repair.

[0034] In a further aspect, the invention provides a laminated chemical
processor, comprising: a plurality of sheets in a stack; the stack having
mutally perpendicular dimensions of height, width, and length; wherein
height is the stacking dimension; for an open space within the stack,
length is the longest dimension and width is perpendicular to length;
wherein the stack comprises at least one interface between sheets
wherein, during operation, an internal pressure is applied in an open
space within the stack and at the interface, wherein the open space has
width of at least 0.07 m; and possessing leak resistance such that: when
N2 gas is supplied through an inlet into the void space at said
interface, and wherein an outlet is closed so that pressure increases at
a rate of 30 to 50 kPa/min and pressure in the void space is increased to
790 kPa and held at that pressure for 15 minutes, then returned to
ambient pressure by releasing the N2 gas, and then supplying water at a
rate sufficient to raise the pressure through the inlet at a rate of 300
to 400 kPa/min, and wherein the outlet is closed so that pressure
increases and pressure in the void space is increased to about 3000 kPa
and then continuing to increase pressure at a rate of about 100 kPa/min
to 6000 kPa, and then dropping the pressure at a rate of 250 to 300 kPa
to below 5300 kPa and then continuing to drop pressure to ambient
pressure and draining the water and drying the processor, and again
supplying N2 gas through the inlet at a rate so that pressure increases
at a rate of 30 to 50 kPa/min into the void space at said interface, and
wherein the outlet is closed so that pressure increases and pressure in
the void space is increased to 790 kPa and the inlet closed so that no
more gas enters the void space, the device leaks less than 100 kPa over
the following 15 minutes.

[0035] The invention includes processors possessing the claimed leak
resistance; not merely processors that have undergone the testing
protocol. More preferably the processor has a leak resistance of less
than 30 kPa over the following 15 minutes, and in some embodiments in the
range of 1 to 50 kPa. In some preferred embodiments, the open space has a
width of at least 0.1 m, in some embodiments a width of at least 0.3 m.
The processor can be any shape; and in some embodiments the processor is
comprised of a stack of rectangular sheets while in some other
embodiments, the processor is comprised of a stack of circular sheets.

[0036] Preferably, the processor does not have an endplate that has a
thickness greater than 3 cm, preferably not greater than 1 cm, and in
some embodiments not greater than 0.5 cm. Preferably, the processor has a
width and a length of at least 0.3 m; in some embodiments at least 0.5 m.
The invention includes any combination of features described throughout
this description; for example, a processor having a width and a length of
at least 0.3 m and which does not have an endplate that has a thickness
greater than 3 cm. The interface can be planar but it not necessarily
planar.

[0037] In some embodiments, the device comprises more than 0.1 km of
internal linear weld, in some embodiments more than 1 km of internal
linear welds and an exoskeleton. Preferably, the laminated chemical
processor is held together by the exoskeleton and welds. Preferably, the
laminated chemical processor is not diffusion bonded or brazed and does
not have gaskets. Clamps are not needed to hold together the laminated
chemical processor and due to its leak resistance (which is not due to
clamps), the processor does not need to be within a pressure containment
vessel. In some preferred embodiments, at least 60 vol % (in some
embodiments at least 80 vol %) of the entire laminated chemical processor
is composed of microchannels and other void space.

[0038] In the leak resistance test described above, the statement that the
"outlet is closed" means that N2 is trapped within the void space except
for leakage out through the interface between sheets. Further, it should
be understood that this test applies to a single interface or the
averaged sum of all interfaces served by the inlet. The device meets the
test if at least one fluid circuit having the specified parameters meets
the test, preferred devices have at least 2 fluid circuits that meet the
test, more preferably, all fluid circuits meet the test (for example, if
the device has two fluid circuits each served by one inlet and one
outlet, both circuits meet the test). The device is at ambient pressure
except for the areas of the device connected to said inlet.

[0039] The invention also includes a laminated chemical processor having
an exoskeleton and having one or more (including any combination) of the
features described herein. A continuous unattached span within an
internal pressure boundary is the minimum distance between a given point
of attachment between laminae within a given pressure-exposed interface
in the laminated device to an adjacent point of attachment between those
same laminae. In preferred embodiments the exoskeleton is welded to the
device, while in other embodiments the exoskeleton is held by brazing,
gluing, or other means.

[0040] The exoskeleton is superior to clamps. Clamps can be more easily
removed (exoskeletons need to be removed by cutting or grinding).
Furthermore, in an exoskeleton-welded reinforcement members can have a
rectangular cross section oriented with the longer side parallel to the
direction of load application to provide increased stiffness to resist
bending stress. This permits the use of thinner shell plates and reduces
the weight and cost of material required to support equal loads. Clamps
having thick plates with threaded fasteners could be used in place of the
exoskeleton; however, the plates would need to be strong enough for the
bending stress since the threaded fasteners would not be loaded in this
direction. The threaded fasteners would need to be strong enough for the
full tension stress caused by the force created by the pressure acting on
the plates. The exoskeleton provides additional support to the plates in
both cases. Furthermore, clamps would be more likely to loosen and fail
during repeated cycling.

[0041] The invention also includes a method of operating a laminated
chemical processor, comprising: passing a gas into an inlet of the
processor to increase pressure inside the processor to a first pressure;
optionally detecting leaks and optionally repairing the leaks; releasing
the gas; passing a fluid into the processor to increase pressure inside
the processor to a second pressure, wherein the second pressure is higher
than the first pressure; removing the fluid; passing a gas into an inlet
of the processor to increase pressure inside the processor to a third
pressure, wherein the second pressure is higher than the third pressure;
and measuring leaks while the processor is held at the third pressure. In
some preferred embodiments, the fluid is a liquid. This method is
superior to a technique of a single step of loading a pressurized fluid
into a device and testing for leaks.

[0042] In yet another aspect, the invention provides a laminated device
comprising: a stack of sheets joined by welding; the stack of sheets
comprising a core stack of sheets joined by welding along the perimeter
of the sheets; and a strain relief joint within the stack of sheets;
wherein the strain relief joint comprises two adjacent sheets that are
held within the stack but are substantially not joined to each other
along the perimeter of two adjacent sheets.

[0043] Throughout this disclosure, "adjacent" means directly adjacent with
no intervening sheets.

[0044] The invention includes any method of using any of the apparatus
described herein; for example, a chemical process using any of the
apparatus described here. Likewise, the invention includes any apparatus
for conducting any of the methods described in this application. The
invention further includes any combination of the methods and/or
structures mentioned herein. The sheets and inserts (if present) are
preferably all comprise metal. In the finished devices, the metal can be
coated with protective coatings and/or catalyst coatings such as a porous
metal oxide layer having a catalyst metal dispersed on the metal oxide.

[0045] The invention is intended to include, in various alternatives, any
of the broad concepts and/or specific features that are described herein
and can be reasonably inferred by the person skilled in this technology.
For example, the inventive apparatus can have any of the combination of
features described herein.

[0046] The invention is not limited to the specifically concepts
identified above, but includes any of the methods, systems, and
apparatuses described herein. The invention includes any feature or any
combination of the features mentioned herein. The invention also includes
methods of chemical processing (including, for example, heat transfer,
chemical reactions, the Fischer-Tropsch (FT) synthesis reaction) and, for
example, includes one or more (including any permutation) of the
conditions, conversions, etc. that are mentioned herein. Where a process
is described with reference to graphs or tables, the invention includes
processes that have values within +/-20%, more preferably about 10%, more
preferably about 5%, and in some embodiments within about 1% of the
conditions, ranges, and/or values described herein. For example, the
invention includes a method of FT synthesis operating with a contact time
in the range of about 90 to about 278 ms with a CO conversion between
about 58 and about 73% and a methane selectivity of between about 8 and
about 34% (the term "about" would include values within +/-20%); the
invention includes methods that are further defined by the device
structures; the invention may alternatively be defined as a system which
includes both apparatus features and fluid compositions and/or
conditions--for example, a system could be apparatus containing hydrogen
gas and carbon monoxide at a temperature above 180° C.

GLOSSARY

[0047] An "assembly" is two or more plates joined together to form a
laminate. An assembly is typically made up of plural "subassemblies" and
can be a functioning device or a precursor to a device. A "subassembly"
is an "assembly" that is (or is intended to be) a component of a larger
laminated assembly. In some preferred embodiments, an assembly is fully
sealed except for inlets and outlets. An assembly is not required to be a
fully functioning device; for example, it may be a precursor or
intermediate product to a fully functioning device. For example, in some
cases, a secondary trimming step is required to open inlet and outlet
flow passageways. In some embodiments, an assembly is made up of plates
having width and length dimensions of a finished device; in some other
embodiments, assemblies can be cut into multiple subassemblies or,
alternatively, joined to form a larger assembly. In some preferred
embodiments, an assembly (or subassembly) has a thickness of 1 cm or
less; in some preferred embodiments, a thickness of between 0.1 and 1.0
cm; in some embodiments a thickness of between 0.2 and 0.4 cm. It is
preferred that plates within an assembly are substantially flat and that
the assembly has flat top and bottom surfaces.

[0048] Throughout this disclosure, the terms "plate," "sheet," "laminae,"
and "shim" are used interchangeably. Plates have a thickness of 1 cm or
less; preferably 0.5 cm or less; more preferably 0.3 cm or less; and
typically have a thickness of at least 0.02 cm.

[0049] An "exoskeleton" is an array of stiffening members which are held
(for example, via welding) in intimate contact with the major exterior
faces of the endplates of a laminated chemical processor, and extend
continuously along the endplate which intervenes between an internal
pressure boundary and external pressure boundary of the array of
stiffening members. The stiffness of the members of the array is such
that they resist bending in the stacking direction (i.e. the direction
orthogonal to the plane of the laminae). An exoskeleton is not a clamp
and does not require screws or bolts.

[0050] A "gap" is the smallest dimension of a microchannel. Typically, in
a laminated device, the gap is in the stacking direction (i.e., the
height). Where the term "gap" is used, preferred embodiments can be
described instead as the height of a microchannel.

[0051] A "microchannel" is a channel having at least one internal
dimension (wall-to-wall, not counting catalyst) of 10 mm or less,
preferably 2 mm or less, and greater than 1 μm (preferably greater
than 10 μm), and in some embodiments 50 to 1500 μm, with 500 to
1500 microns especially preferred when used with a particulate form of
catalyst; preferably a microchannel remains within these dimensions for a
length of at least 1 cm, preferably at least 20 cm. In some embodiments,
in the range of 5 to 100 cm in length, and in some embodiments in the
range of 10 to 60 cm. Microchannels are also defined by the presence of
at least one inlet that is distinct from at least one outlet.
Microchannels are not merely channels through zeolites or mesoporous
materials. The length of a microchannel corresponds to the direction of
flow through the microchannel. Microchannel height and width are
substantially perpendicular to the direction of flow of through the
channel. In the case of a laminated device where a microchannel has two
major surfaces (for example, surfaces formed by stacked and bonded
sheets), the height is the distance from major surface to major surface
and width is perpendicular to height. In some preferred embodiments of
this invention, microchannels are straight or substantially
straight--meaning that a straight unobstructed line can be drawn through
the microchannel ("unobstructed" means prior to inserting solid
catalysts, sorbents, or other separate solid materials). Typically,
devices comprise multiple microchannels that share a common header and a
common footer. Although some devices have a single header and single
footer; a microchannel device can have multiple headers and multiple
footers. Microchannels are also defined by the presence of at least one
inlet that is distinct from at least one outlet--microchannels are not
merely channels through zeolites or mesoporous materials. The height
and/or width of a reaction microchannel is preferably about 2 mm or less,
and more preferably 1 mm or less. The sides of a microchannel are defined
by reaction channel walls. These walls are preferably made of a hard
material such as stainless steel, or a Ni-, Co- or Fe-based superalloy
such as FeCrAlY. The process layers may comprise a dissimilar material
from the heat exchange channels, and in one preferred embodiment the
process layers comprise copper, aluminum or other material with a thermal
conductivity greater than 30 W/m-K. The choice of material for the walls
of the reaction channel may depend on the reaction for which the reactor
is intended. In some embodiments, the reaction chamber walls are
comprised of a stainless steel or Inconel® which is durable and has
good thermal conductivity. Typically, reaction channel walls are formed
of the material that provides the primary structural support for the
microchannel apparatus. Microchannel apparatus can be made by known
methods, and in some preferred embodiments are made by laminating
interleaved plates (also known as "shims"), and preferably where shims
designed for reaction channels are interleaved with shims designed for
heat exchange. Some microchannel apparatus includes at least 10 layers
(or at least 100 layers) laminated in a device, where each of these
layers contain at least 10 channels (or at least 100 channels); the
device may contain other layers with fewer channels.

[0052] In some apparatus, process channels contain catalyst particles.
Preferably, the particles have a size (largest dimension) of 5 mm or
less, in some embodiments, 2 mm or less. Particle size can be measured by
sieves or microscopy or other appropriate techniques. For relatively
larger particles, sieving is used. Particulate materials included in
process channels may be catalyst, adsorbent, or inert material.

[0053] Heat exchange fluids may flow through heat transfer channels
(preferably microchannels) adjacent to process channels (preferably
reaction microchannels), and can be gases or liquids and may include
steam, liquid metals, or any other known heat exchange fluids--the system
can be optimized to have a phase change in the heat exchanger. In some
preferred embodiments, multiple heat exchange layers are interleaved with
multiple reaction microchannels. For example, at least 10 heat exchangers
interleaved with at least 10 reaction microchannels and preferably there
are 10 layers of heat exchange microchannel arrays interfaced with at
least 10 layers of reaction microchannels. In some preferred embodiments,
when there are "n" layers of process microchannels then there are "n+1"
layers of heat exchange layers whereby the heat exchange layers flank all
process layers. Each of these layers may contain simple, straight
channels or channels within a layer may have more complex geometries. The
invention includes systems that are comprised of both apparatus and
fluids present in the apparatus. In "Bonding," a heating process is used
for joining pieces in which there is diffusion of elements from one piece
to another resulting in a joined article with diffused elements near the
interface (or near what used to be the interface before bonding).

[0054] Brazing uses an interlayer sandwiched between parts, the interlayer
has a lower melting point than the parts.

[0055] Welding uses heat to join or seal parts. Unlike brazing, welding
does not require a lower melting material, although it is recognized that
a weld may use a weld wire of the same material or similar material which
may have a slightly lower melting temperature, but a joint is also
referred to as a welded joint where the seal is at the periphery of a
laminated device, with some weld penetration depth at the periphery
rather than throughout the article. A "weld" in a finished piece can be
identified by the skilled worker--for example, a metallurgist can
identify a weld by microscopic inspection or other techniques known in
the art.

[0056] "Joining" includes welding, bonding, adhesives, brazing. Joining is
any process that binds two or more pieces together.

[0057] A "substrate assembly" is composed of a plurality of sheets that
are attached to each other to form a cohesive, laminated stack. A
"substrate assembly" is sometimes termed a panel, and may be comprised of
top and bottom sheets defining a flow path, and, more typically comprises
numerous sheets in a stack defining numerous flow paths.

[0058] The invention also includes methods of conducting unit operations
within the apparatus described herein. "Unit operation" means chemical
reaction, vaporization, compression, chemical separation, distillation,
condensation, mixing, heating, or cooling. A "unit operation" does not
mean merely fluid transport, although transport frequently occurs along
with unit operations. In some preferred embodiments, a unit operation is
not merely mixing.

[0059] Microchannel reactors are characterized by the presence of at least
one reaction channel having at least one dimension (wall-to-wall, not
counting catalyst) of 1.0 cm or less, preferably 2 mm or less (in some
embodiments about 1 mm or less) and greater than 100 nm (preferably
greater than 1 μm), and in some embodiments 50 to 500 μm. A channel
containing a catalyst is a reaction channel. More generally, a reaction
channel is a channel in which a reaction occurs. The length of a reaction
channel is typically longer. Preferably, the length of a reaction channel
is greater than 1 cm, in some embodiments greater than 50 cm, in some
embodiments greater than 20 cm, and in some embodiments in the range of 1
to 100 cm.

[0060] "Press-fit" describes the manner in which a fin (preferably a
copper waveform) is disposed within a space within the apparatus. A
press-fit fin is held in place by being compressed or snug within a void
within a device or subassembly. Although a small amount of tack welding
can be present; a press-fit fin is not brazed or welded at all contact
points into position. Preferably, a press fit fin is not held in position
by any adhesive or any such chemical bonding.

[0061] Open Space--refers to a space within the processor in which there
are no bonded internal supports that resist tension. The open space may
contain ribs or other structures that provide support in compression, but
these structures are not bonded on both sides of the interface and thus
do not resist tension. An "open space" may be present as part of a larger
space; however, in preferred embodiments, the laminated device is welded
or otherwise joined only on the periphery.

[0062] Void space is space within a device that is accessible to N2 gas
passed into one or more inlets of the device. The volume of void space
can be measured by evacuating the space for at least 10 seconds and then
passing N2 gas into the space and measuring the quantity of N2 gas
filling the space.

[0063] Internal linear weld--welds that join two or more laminates
together within the perimeter of an externally perimeter welded device.

[0064] As is standard patent terminology, "comprising" means "including"
and neither of these terms exclude the presence of additional or plural
components. For example, where a device comprises a lamina, a sheet,
etc., it should be understood that the inventive device may include
multiple laminae, sheets, etc. In alternative embodiments, the term
"comprising" can be replaced by the more restrictive phrases "consisting
essentially of" or "consisting of.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] FIG. 1 illustrates some elements from which a process layer can be
assembled.

[0072] FIG. 7 is a photo illustrating a fillet weld added (picture at the
right) to create a more uniform framework for the catalyst retention
assembly. The irregular fin shape shown in the right side of FIG. 7 is
caused by compression.

[0075]FIG. 10 shows the transition to partial boiling and the stable
performance of the all welded reactor.

[0076] FIG. 11 shows a plot of thermal runaway in the inventive all welded
reactor at a contact time of 70 ms.

[0077]FIG. 12 illustrates pre-cambering with the pre-camber in parallel
with the coolant channels to reduce curvature.

[0078] FIG. 13 is an autopsy photo of a press fit fin adjacent to the
ridges formed from the laser welding process. The fin contacts on the
ridges and then a small crevice crack can be observed between the fin and
the heat transfer wall.

[0079] FIG. 14 shows laser weld lines that join the top of the ribs
between parallel and adjacent coolant channels formed in the bottom
plate.

[0088] The described invention provides methods of making devices, and
devices which can be made by the methods. The invention further includes
methods of conducting unit operations in the devices. The unit operations
may include chemical reactions, phase change, mixing, heat transfer, and
separations. The devices may be microchannel or they may be used for
devices with larger characteristic dimensions. The characteristic
microchannel dimension is defined as 10 mm or less, with a range from
about 0.001 mm to 10 mm, with a preferred range of 0.01 mm to 2 mm, and
in some embodiments from 0.1 to 2 mm.

[0089] In some embodiments, a method includes a first step of forming a
subassembly from at least two sheets, a bottom sheet and a top sheet (the
bottom sheet may contain etched channels--alternatively, a sheet with
through channels may be disposed between top and bottom sheets. In some
embodiments, the subassembly may be made from three or more sheets. There
may be small leaks but a fluid traversing through the first subassembly
substantially stays within the first subassembly. In a second step, the
first subassembly is stacked adjacent to a process layer and the
subassembly and process layer are press fit into thermal contact to form
an assembly that includes at least two or more fluid passageways.

[0090] One method of joining a subassembly creates a short stack of layers
that comprises two or more layers to create fluid passageways. In
alternate embodiments, more than two layers may be joined to create an
array of parallel fluid passageways or a subassembly that enables fluid
passageways for two or more fluids.

[0091] As an example of one embodiment for forming a first subassembly, a
shim or laminae containing preformed channels (the channels may be formed
by etching) is joined with a top plate. The edges of the subassembly are
substantially hermetically sealed along the edges to prevent a fluid from
leaking out the sides and maintaining the continuity of flow passage such
that more than 95% and preferably 99% and more preferably still 99.9% of
fluid that enters from a first inlet leaves the subassembly from a first
outlet, rather than leaking out through the sides or other pathways where
flow is not intended. In alternate embodiments, there may be more than
one inlet and/or outlet that is defined by the laminate geometry.

[0092] The laminates are preferably also sealed along the top and or
bottom face of the subassembly along corridors of continuous metal or
material; in some preferred embodiments, at least 50% of corridors have
continuous seals in the length direction on at least the top and/or
bottom face; typically, the seals are along channel walls that separate
channels. The joining may only occur in regions where when stacked in a
subassembly, metal is in contact between the layers. It is understood
that regions comprising a flow channel or a void for fluids to traverse
after the device is manufactured would not be closed. It takes two
materials in contact to form a seal. It is also understood that the
joining of the subassembly along one or more faces of the subassembly may
be continuous along the flow path or intermittent as required by the
structural operating requirements of a device. Fluid may leak or traverse
from one parallel channel to the next within a first subassembly when
tested as an operational device or during quality control checks prior to
operation. This small amount of transverse flow is less than 20% of the
per channel flow and more preferably less than 10%, and still more
preferably 2% or less; these percentages can be based on traverse flow
averages over all channels, or traverse flow from any selected channel.

[0093] The joining of a subassembly comprises at least two layers, but
could include three, or more layers. In one embodiment, twenty or more
layers are joined in a subassembly. Methods for joining a first
subassembly include but are not limited to laser welding, resistance
welding, friction stir welding, ultrasonic welding, diffusion bonding,
brazing or diffusion brazing or transient liquid phase brazing, adhesive
joining, reactive joining, mechanical joining, and the like. The use of
laser welding is a preferred embodiment, with specific types of laser
welding (including fiber lasers and Yb fiber lasers in particular because
of their low energy input which limits the amount of metal distortion
after joining).

[0094] The method for joining the face of the subassembly may be the same
or different than the method for sealing the edges of the subassembly. In
one embodiment a fiber laser is used to seal along the perimeter and in
another embodiment a pulsed laser is used. Other welding or joining
methods may be used as well to seal along the perimeter (except for
regions where flow passageways enter or exit a layer).

[0095] The joined or sealed subassembly is preferably checked for quality
("QC'd") prior to stacking into an assembly. Every subassembly may be
evaluated or a statistical sampling of subassemblies may be QC'd or a
random sampling of subassemblies may be evaluated for quality. A quality
check may include a pressure test to check for leaks, a flow test to
check for pressure drop or a dye test to check for residence time
distribution which may be suggestive of flow between otherwise intended
sealed interior parallel channels.

[0096] The joined or sealed subassemblies may then be joined into an
assembly by interleaving or interspersing joined subassemblies with a
second subassembly or a second array of fluid passageways to create a
device with two or more sets of fluid passageways.

[0097] A fluid passageway may include a waveform or fin structure or
alternate structure useful for chemical processing such as foams, felts,
wads, cellular structures such as aerogels, honeycombs, and the like. In
some preferred embodiments, the waveform or fin structure creates
channels or chambers that have an aspect ratio (height to width) greater
than one, where the height is the distance between two subassemblies and
width is the distance between repeating fins or adjacent legs (wave
surfaces) of the waveform. In an alternate embodiment, the second fluid
passageway may contain any thermally conductive structure.

[0098] In a preferred embodiment the second fluid passageway are process
channels and the first subassembly comprises heat transfer channels,
although in some embodiments this functionality may be reversed.

[0099] An example of elements that can be used to construct a process
fluid passageway is shown in FIG. 1, where a waveform is created from
planar foils. The exterior of the fluid passageway is sealed with the use
of edge strips (also defined as perimeter strips or p-strips) or side
bars and may also include the use of support strips (s-strips).

[0100] The first subassembly is placed or stacked between a layer of the
second fluid passageway (shown as a waveform layer). This is shown in
FIG. 2. There may be a single contiguous second fluid passageway or
multiple contiguous fluid passageways (three shown in the FIG. 2) stacked
at each layer for the second fluid passageway.

[0101] A process waveform may be joined to the first subassembly with the
use of welding along apex of the fins or with thermally connected
adhesives or other materials that enhance the thermal conductivity of the
contact between the first subassembly and the second fluid passageway. In
one embodiment, the two layers are pressed into each other during
stacking and welding with no additional material added to enhance the
thermal connection (this embodiment, with no brazing or weld joining
parts, is termed "press-fit"). In another embodiment, additional material
is added to reduce the contact resistance between the first subassembly
and the second fluid passageway. In another embodiment, the thermal
contact during chemical processing is enhanced by the use of a multiphase
process, where the small clearance or gaps between the press fit process
structure and the subassemblies are filled with a liquid during
processing via capillary forces. The liquid may preferentially fill the
gaps and enhance the conductivity of the composite structure when
operated as a chemical processing unit.

[0102] After stacking the hybrid stack which includes both a first
subassembly and a second fluid passageway, the inventive device is joined
to form a stack by a method such as, but not limited to, exterior
welding, adhesives, and reaction joining. The stack welding may use
different types of welding methods, comprising TIG, MIG, laser welding,
electron beam welding, among others. The exterior welding is
preferentially automated for reproducibility and cost reduction.
Soldering could also be an option for joining the perimeter if the
service temperature and pressure of the chemical processor were
sufficiently mild as to be conducive with solder.

[0103] Prior to joining the final assembly, the stack may be compressed to
bring the layers into contact and reduce the voids between layers where
the final device joining will occur. Compression may occur, for example,
with the use of a clamped fixture applying a load with a bolt assembly or
through the use of an external press to apply a load to the stack. The
press-fit waveform may deform during compression, and may remain deformed
after the compression is removed.

[0104] Subassemblies may require flattening prior to stacking. One method
of flattening includes roll flattening of a laser welded subassembly
using a leveling machine. This method reduced the deformation when used
with 6''×24'' (15 cm×60 cm) panels. These panels had a one
dimensional deformation--along the length of the weld lines. Roll
flattening was less successful with a 24''×24'' (60 cm×60 cm)
subassembly, where the part had deformation in two directions (a bowl
shape or three dimensional parabolic-like shape). A conventional leveling
machine was used to flatten the distorted part, but it resulted in
breaking the laser welds. An unconventional and gentle hand roller was
used to less aggressively bend the distorted part to a more flat state.
The unconventional hand roller resulted in some reduction in deformation
but did not reduce the part to a substantially flat state, wherein
substantially flat is defined by the part sitting up no more than 1 cm at
any corner when laying on a flat surface. Thus, gentle flattening may
produce a superior device, especially for subassemblies that have
differing width and length (i.e., non-square subassemblies). In some
preferred embodiments, flattening is conducted on subassemblies having
widths of about 15 cm or less; in some embodiments about 10 to 20 cm
widths.

[0105] V-grooves are advantages between subassemblies since weld fillets
can be applied to fill the V-grooves. The subassembly may protrude out
slightly from the side bars or edge strip region. In an alternative
embodiment, the subassembly is substantially flush with the edge strip.
Substantially flush means within 5 or less increments of subassembly
thickness. As an example, if a subassembly were 0.01'' (0.025 cm) thick
then the edge of the subassembly would neither protrude nor be recessed
more than 0.05'' (0.125 cm) from the edge of the edge strip. For a 0.06''
(0.15 cm) subassembly, the offset from a flush edge is no more than about
0.3'' (0.75 cm) with a preferred degree of offset no more than 0.06''
(0.15 cm) from even, e.g. either protruding 0.06'' (0.15 cm) or recessed
0.06'' (0.15 cm) as a preferred embodiment.

[0106] A key advantage of this hybrid method of manufacturing is to reduce
the surface preparation requirements for diffusion bonding and or
brazing. Surfaces must be very clean, flat, and with tight tolerances for
close fit up for a quality diffusion bond and or braze. Elimination of
the brazing and or bonding step also eliminates the need to take the
large device to a high temperature as required for diffusion bonding and
or brazing. The energy required to heat and cool a large device is
significant, as is the time required to heat and cool a large device to
bonding or brazing time without incurring undue mechanical thermal strain
and resulting deformation. For a device made from stainless steel
composed of primarily planar interior laminae, an internal thermal
gradient from the outermost corner to the center point should be less
than about 30° C. above 500° C. to prevent mechanical
deformation of the layer. For a device with a cross section greater than
0.5 m×0.5 m, it may take several days to heat and several days to
cool the device when brazed or bonded in a vacuum-based thermal process.
The required processing time and surface preparation of parts increases
the overall cost of a reactor.

[0107] The inventive method for device manufacturing avoids the need for a
diffusion bond and or braze step of a reactor. The inventive method can
result in a reactor manufactured with a higher quality for a lower cost
and in less time.

[0108] A surprising result from the inventive press fit device is the
effect of contact resistance between the layers. The press fit of layers
does not insure intimate thermal contact, which is further exacerbated as
the size of the device increases and the starting part flatness is less
than perfect. Heat is moved between the first subassembly and the second
fluid passageway through a lower quality contact region separating the
fluid streams. In a diffusion bonded or brazed device, each layer is in
intimate thermal contact by the very nature of bonding and or brazing,
whereas local surface roughness and or part irregularities or initial
deformation will reduce the efficiency of heat transfer between the
layers.

[0109] The importance of the thermal contact between the layers will
depend upon the process operating requirements for the reactor or device.
In some embodiments, the interior voids between the two layers will be
filled in by the process fluids during operation. In another embodiment,
a thermally connecting material such as an adhesive or putty or liquid or
deformable solid such as a graphite or comparable interlayer may be
introduced into the press-fit layer to reduce the contact resistance
between the two fluid layers (at least one of which is a press-fit
layer).

[0110] In some embodiments, no intervening thermal contacting layer is
required. The Fischer Tropsch reaction was tested in an inventive reactor
without the use of an intervening layer to enhance thermal contact
between a process side waveform and a coolant side laser welded
subassembly. The performance substantially matched that measured from an
all brazed reactor of similar design.

[0111] It is also envisioned that reactions or unit operations involving
either hydrogen and or a liquid, including but not limited to
hydrogenation, hydrocracking, or hydroprocessing reactions, would not
require an intervening thermally conductive layer between the first
subassembly and the second fluid passageway. These fluids have good
thermal conductivity and if these fluids fill the voids, good thermal
conductance can be obtained. The liquids will all have a sufficient
capillary pull to wick into the voids between the fin and the adjacent
heat transfer surface. Further, it is noted that the surface tension of
oils is substantially lower on copper than stainless steel, which further
enhances the capillary pull of an oil or wax in the case of a Fischer
Tropsch reactor, into the voids between the copper and stainless (or
other metal) during reaction. The higher surface tension of oil or
liquefied wax on stainless may not have the same effect or may require
substantially smaller gaps to wick the liquid into the voids. It is
envisioned that the copper fins will also be more forgiving for
manufacturing irregularities.

[0112] It is envisioned that reactions involving oxidation reactions may
require an intervening thermally conductive material. In one embodiment,
a washcoated catalyst or other retaining fluid on the second fluid
passageway may also serve as the intervening thermally conductive
material as it fills the voids between the two layers to assist with heat
transfer and thermal control of the reaction.

Strain Relief Joint

[0113] A strain relief joint, made up of two plates welded together, can
be added to the stack to reduce the strain imparted to the welds joining
adjacent layers in the core. The joint is designed to open (expand) as
the reactor becomes pressurized during operation. By doing so, the seal
welds located on the reactor's outer surfaces remain unstrained which
increases the life of the unit.

[0114] The expansion joint is made up of two metal plates, typically of
the same width and length of the stack. For example, in the device
described elsewhere in this description, the plates are ˜24'' (60
cm) wide×24'' (60 cm) long to match the dimensions of the other
plates in the stack. Preferably, the lower plate is thinner than the top
plate in the strain relief joint; for example, the base plate (i.e., the
plate coplanar with and contacting the stack) can be ˜0.25'' (0.625
cm) thick and the top plate (the plate nearer the exterior major surface)
about 0.04'' (0.1 cm) thick. In some preferred embodiments, the base
plate contains a plurality of holes and the top plate is featureless. The
plates are placed on top of one another and aligned at the edges. The
plates are then welded via a laser welding process. The edges of
expansion joint plates are not continuously welded; this allows movement
of the plates during operation of the device. Preferably, the weld
pattern is such that the edges of the plates are not joined except at the
corners. This allows the edges to separate during operation if needed to
take up any expansion of the reactor without straining the seal welds on
the reactor and to isolate the different internal streams from one
another. The holes in the base plate allow the welds to be individually
checked for leakage prior to assembling into a reactor. Once the
expansion joint has passed the qualification test, the base plates holes
can be filled in using a standard TIG welding process.

[0115] Preferably, two expansion joint assemblies are used in a completed
reactor core; one at the top of the core and one at the bottom.
Preferably, one plate of the strain relief joint is placed against the
reactor core and welded to a coolant subassembly all around the
perimeter.

[0116] During operation the reactor is pressurized. The pressure results
in some elastic stretching of the external supports. Without strain
relief joints being present, this would lead to a corresponding stretch
of the reactor core itself and result in stress induced strains
developing in the seal welds. With the expansion joints present, the
elastic stretching is taken up by the opening of the joints which
alleviates the strains on the welds

[0117] An optional step of welding on a halo (which is a made from one
contiguous hollow square or rectangular metal ring or from two or more
parts welded together to form a contiguous ring that protrudes above the
face of the core. The halo creates a structure intermediate to the device
and the final operational manifolds (macromanifolds) such that during
refurbishment, the connection between the macromanifold and the device
can be cut apart and rewelded or joined for a subsequent operational
period. This use of a halo is particularly advantageous as a means to
remove or refurbish a catalyst contained within the reactor core. Halos,
devices comprising halos, methods of making devices having halos, and
methods of using devices having halos are additional inventive aspects of
the invention.

EXAMPLES

Example 1

Welded Subassembly--Welded Reactor--Press Fit Conductive Fin

[0118] A welded reactor was fabricated and operated to validate the
equivalent performance to a brazed reactor using Fischer Tropsch as a
test reaction. The reactor operated for more than 2000 hours time on
stream and demonstrated that a press-fit contact of a catalyst containing
process fin against the subassembly was sufficient for reactor
performance and matched the performance from a brazed reactor of the same
design.

Device Description

[0119] A two-layer Fischer Tropsch all-welded device was designed and
fabricated to validate the inventive manufacturing process. The
multichannel microreactor design consists of two process repeated units
interleaved between three coolant repeated units. The coolant channels
are in a cross-flow orientation to the process channels.

[0120] The process channels are created from a copper waveform 15.75 cm
(6.2 inches) long by 7.62 cm (3 inches) wide and 0.635 cm (0.256 inches)
high. The thickness of the waveform is 0.015 cm (0.006 inches). The
resulting device has 274 process channels in two layers. Each of these
channels has average dimensions of 0.095 cm (0.0375 inches) width, 0.635
cm (0.25 inches) height and 7.62 cm (3 inches) length. The fin was
oversized by 0.006'' (0.015 cm) from the nominal dimension of the
adjacent edge strips to insure excellent thermal contact.

[0121] The coolant channels of the device comprised of laser welded
subassemblies joined to a top plate with a Yb fiber laser (IPG model
YLR-600-SM: 600-Watt Ytterbium Fiber Laser, 1.07 micron wavelength) with
a weld thickness between 50 and 150 microns through a 500 micron top
plate penetrating into but not breaking through a 1000 micron bottom
channel plate. The subassemblies are created from two shims which include
a top or cover sheet or walls accompanied by a channel shim which
contains flow channels for the heat transfer fluid. These coolant
subassemblies stacked in the ˜3'' L×˜10''
W×˜2.7'' H (8 cm×25 cm×7 cm) device and were
sealed to the perimeter with fusion and fillet welds.

[0122] After weldment of the core components, the device was cleaned and
loaded with 66.5 grams of a high activity cobalt catalyst obtained from
Oxford Catalysts, Limited and silicon carbide sourced from 120 grit
material supplied by Atlantic Equipment Engineers.

The final fabrications steps consisted of header and footer weldment (for
the coolant and process channels for external connections to macroscale,
i.e. larger piping) and support weldment. The support weldment was a
structural necessity for this design which also enables the device to
operate safely without the need for a pressure containment system (PCS).

Core Component Fabrication

[0123] The all-welded reactor has two Process layers that comprise a
copper waveform and two stainless steel edge strips each. The three
Coolant layers are interleaved with the process layers and are fabricated
as subassemblies via laser welding a stainless steel top plate or wall
and a stainless steel channel shim together. The wall shims were sheared
to size from 0.020'' (0.05 cm) thick stock SS sheet material. The coolant
shims have non-straight and straight channel features that are formed via
partial PCM (Photo Chemical Machining) in 0.040'' (0.1 cm) thick SS
sheet, creating 0.020'' (0.05 cm) deep by 0.100'' (0.25 cm) wide channels
with 0.040'' (0.1 cm) ribs for the straight channels and 0.015'' (0.0375
cm) deep by 0.017'' (0.0425 cm) wide channels for the non-straight
section. The non-straight section was made with a wavy or serpentine
pattern with 22 turns. The laser welding was done on each rib, the full
length of the shim, to create a seal between channels as well as between
the outermost channels and the perimeter to seal the channels from the
exterior. The subassemblies were then leak checked. Having the capability
to leak check subassemblies enabled identification and repair of leaks
prior to assembly in a device and avoiding fabrication of a failed
device. Another advantage of having the coolant layers pre-fabricated as
subassemblies is the reduction of parts to stack in an assembly by at
least about 20%.

[0124] The edge strips on the Process side were fabricated from standard
material thickness (nominal 0.250'' thick) (0.625 cm) and required
minimal machining, only a cut to length and width and edge chamfering.
The copper waveforms were fabricated from a standard fin forming process
where thin coils are regularly bent to produce a repeating fin structure.
The fins were made with a 0.256'' (0.64 cm) height. The endplates
required minimal machining as well to achieve the desired length, width
and chamfering. All parts do not require the tight thickness tolerances
associated with brazed devices and thus stock material can be used.

Device Assembly for Example 1

[0125] The core of the device (i.e. the Process and Coolant layers
sandwiched between two endplates) is created by stacking components to
create interleaved process and coolant layers. The number of Process
layers is determined by desired capacity of FT product while the number
of Coolant layers is one more than the number of Process layers such that
each Process layer has a Coolant layer on both sides. During the stacking
process a fixture is required to align the parts, as well as maintain
alignment throughout the assembly and the initial welding steps. A clamp
fixture was designed to create a platform to stack on as well as to
secure the stacked core for transport to the welding step. The clamp
fixture consists of two plates shaped like an elongated plus sign. Each
has four (4) slots to fit 1/2'' (1.25 cm) all-thread rods. A support
plate was placed under the bottom clamp to create room for the all-thread
end and nut on the bottom-side. For alignment of the Process faces, four
straight edges were held in place on either side of the clamp fixture
with c-clamps. A fifth straight edge was used to align one of the two
coolant faces.

[0126] With the stacking and alignment fixture setup, the first step is to
place an endplate on the clamping fixture, centering it between the
Process face straight edges. The Coolant face straight edge is then put
in place before stacking the first layer. The first layer that was
stacked was a coolant subassembly. Process layers are disposed between
two coolant layers. The subassembly is lowered onto the endplate and slid
into place against the coolant face straight edge and centered between
the chamfers on the endplate (FIG. 6). Once alignment is satisfactory,
the first Process layer was stacked on top of the Coolant subassembly. In
this step, the edge strips were flush at the Coolant face. For the fusion
welding, this seals the interface between the edge strips and coolant
subassemblies and the edge strips and endplates. The first edge strip is
placed flush with the coolant straight edge, followed by placement of the
waveform and then the second edge strip. The waveform is placed tight
against the first Edge Strip and centered on the Coolant subassembly. The
second Edge Strip is placed tight against the waveform and it's alignment
with the other Coolant face is checked. If the Edge Strips on both
Coolant faces are aligned within +/-0.010'' (0.025 cm) of the adjacent
layer, alignment was acceptable. This process of stacking coolant
subassemblies and Process layers was repeated one more time, followed by
another Coolant subassembly. The total stack consisted of two (2) Process
layers and three (3) Coolant layers. The last core component to be placed
on the stack was the top endplate. The top endplate is placed flush with
all four Process side straight edges and the Coolant face straight edge.

[0127] There were two weld steps to complete the core welding. The first
weld step made fillet welds along the 2'' (5 cm) wide Edge Strips. There
were six V-grooves on each Process face that are filled with fillet
welds. Curved cutout areas on the clamp fixture allowed access to these
V-grooves to complete this weld step. The initial fillet welds were
designed to stop short of the edge strip end closest to the waveforms to
avoid damaging them. Later the fillet welds were filled in to the inside
edge of the edge strips to match up with the catalyst retention assembly.
The before and after pictures of these fillet welds is shown in FIG. 7.
Once these fillet welds are complete the clamping fixture was removed to
allow access to the coolant faces for the next weld step. On each Coolant
face, there were three coolant subassemblies and hence six seams (one
seam above and below each subassembly) that each had a fusion weld the
full length of the face. The core is then ready for cleaning and
preparation for catalyst loading.

Cleaning and Catalyst Loading

[0128] Prior to catalyst loading, the process side of the device was
cleaned and a catalyst retention assembly welded in place.

[0129] Prior to loading catalyst, a catalyst retention assembly is
inserted and welded in place on one process face to retain the catalyst
while the core is orientated in the vertical position. The catalyst
retention assembly consists of four parts: a screen, a screen retention
ring, foams and a foam retaining ring. The screen functions to retain the
catalyst in the device. The screen retaining ring is a thin SS frame that
holds the screen in place, tight against the process face. A small weld
around the perimeter of the screen retaining ring secures the screen in
place and ensures good catalyst retention in the device. The fillet weld
on the edge strips were also brought up to the inside edge of the edge
strips to provide better catalyst retention. An aluminum shielding plate
may be used to protect the copper waveforms during the perimeter weld on
the screen retaining ring.

[0130] With the catalyst retention assembly in place on one process face,
the catalyst loading was carried out. The loading was a four-step
process. The 4 end channels (1 at each end in each process layer) have
partial fins and were blocked by the screen retaining ring and thus were
considered inactive channels. These channels were filled completely with
Silicon Carbide (SiC), an inert material of nearly the same particle size
as the catalyst in the first loading step. The remaining channels were
loaded with 3-layers: ˜0.665'' (1.6625 cm) SiC at the process
inlet, ˜1.5'' FT (3.75 cm) catalyst bed and ˜0.75'' (1.875
cm) SiC at the process outlet. To obtain the depths of each of the three
layers the materials were loaded into the device in small increments,
followed by pounding the side of the device (endplates) with a rubber
mallet to densify the loaded material. After each incremental load and
densification, gage height pins were used to measure the depth of all
channels. When this process was completed for any given layer, the
material was further densified via ultrasound to obtain as close to PABD
(ex-situ measured packed average bed density of the material) as
possible. Loading was complete when the top layer remained flush with the
edge strips after densification. When the catalyst was not further
densified by ultrasonification, the catalyst bed was considered to be
fully densified. With all three layers (two layers of SiC, one layer of
catalyst) loaded, the catalyst retention assembly was installed and
welded on the open process face of the device using the same procedure as
described earlier for the other process face.

Final Welding for Example 1

[0131] Three final weld steps to completed the device fabrication, viz.
attachment of the process manifolds, coolant manifolds and the Support
plates. Unlike brazed devices, the only internal components for the
all-welded FT device that are sealed throughout are the Coolant
subassemblies. The remaining components (waveforms, edge strips and
endplates) are all only attached to adjacent components at the perimeter.
The Support Plates provide the necessary structural support for the
device to maintain its integrity under the large differential pressures
during operation. The Support Plates also serve to replace the Pressure
Containment Shell (PCS) used for the brazed devices. Two outlets are used
for the coolant, to remove the steam and liquid water separately.

[0132] Process manifolds are constructed from Stainless Steel 304L and are
approximately 9.1'' (22.75 cm) long×2.7'' (6.75 cm)
wide×1.9'' (4.75 cm) deep. An internal pocket with approximate
dimensions of 8.1''×1.7''×1.2'' (20.25 cm×4.25
cm×3.00 cm) totally encapsulates the process waveform opening and
provides support to the catalyst retention mechanism. The manifolds are
welded around the perimeter of the core using a traditional TIG welding
process. One inch diameter tubes extend from the center of both process
manifolds to allow the process gas to enter and exit the core. The
manifolds are designed with a minimum wall thickness of approximately
0.5'' (1.25 cm) in order to support the process pressure during
operation. See FIG. 8.

[0133] The coolant inlet manifold is constructed from Stainless Steel 304L
and is approximately 5.6'' (14 cm) long×2.7'' (6.75 cm)
wide×1.7'' (4.25 cm) deep. An internal pocket with approximate
dimensions of 4.8''×1.9''×1.3'' (12 cm×4.75
cm×3.25 cm) totally encapsulates the coolant inlet channels and is
designed to distribute the coolant equally over the coolant inlet face.
The manifold is welded around the perimeter using a traditional TIG
welding process. One inch diameter tubes extend from manifold to allow
the coolant to enter the core. The manifold is designed with a minimum
wall thickness of approximately 0.38'' (0.95 cm) in order to support the
coolant pressure during operation.

[0134] The coolant outlet manifold is constructed from Stainless Steel
304L and is approximately 5.6'' (14 cm) long×2.7'' (6.75 cm)
wide×4.4'' (11 cm) deep. An internal pocket with approximate
dimensions of 4.8''×1.9''×4.0'' (12 cm×4.75 cm×10
cm) totally encapsulates the coolant outlet channels and is designed to
let the coolant flow exit the reactor core without obstruction. The
manifold is welded around the perimeter using a traditional TIG welding
process. Two 1'' (2.5 cm) diameter tubes extend from manifold from
opposite sides. The top tube allows steam vapor to exit and the bottom
tube allows liquid water to exit. The manifold is designed with a minimum
wall thickness of approximately 0.38'' (0.95 cm) in order to support the
coolant pressure during operation.

[0135] The two coolant manifolds weld directly to the solid metal core
endplates and the process manifolds. By doing so, the core welds are
totally encapsulated within the parameters of the process and coolant
manifolds and therefore, are not directly exposed any exterior surface of
the reactor. See FIG. 9.

[0136] Supports (an exoskeleton) are then added using a traditional TIG
welding process. There are four sets of supports that wrap the reactor in
the vertical (process flow) direction and one additional set that extends
out horizontally over the coolant outlet manifold. Each set of vertical
supports are constructed from two identical pieces of stainless steel
304L which have approximate overall dimensions of 8.8'' (22 cm)
long×3.3'' (8.25 cm) tall×0.25'' (0.625 cm) thick. Each set
of supports are welded together at the points where there ends come into
contact as well as stitch welded to the reactor around its perimeter. The
four sets of supports are separated from each other by approximately 2''
(5 cm) and the first set is located approximately 2.7'' (6.75 cm) from
the edge of the coolant inlet manifold. Whereas the four vertical sets of
supports provide support for the reactor core and process manifolds, the
horizontal set provides additional support to the oversized coolant
outlet manifold. The two horizontal supports are constructed from
stainless steel 304L and are approximately 5.4'' (13.5 cm) long×2'
(60 cm) tall×0.25'' (0.625 cm) thick. They are centered on either
side of the coolant outlet manifold and are welded to that manifold as
well as to the endplates of the core and the outermost vertical supports.

Experimental Setup for Example 1

Process Side

[0137] The flow and composition of synthesis gas (syngas) fed to the
Fischer-Tropsch synthesis microchannel fixed bed reactor was controlled
by setting the flow rates of individual gases (carbon monoxide, hydrogen,
and nitrogen) using Brooks mass flow controllers. The gases were fed
through activated carbon and molecular sieve 13× traps to remove
any impurities. The feed was pre-heated in a stainless steel microchannel
heat exchanger prior to entering the reactor. The reactor was enclosed in
a clam-shell 3000W Watlow heater and further insulated to minimize heat
losses. Operational data was measured using pressure transducers, and
316SS sheath K-type thermocouples.

[0138] The product stream was routed through three collection vessels at
elevated pressure, and cooled in stages to provide rough separation of
lighter from heavier hydrocarbon products along with an aqueous phase.
The first product tank (held at ˜100° C.) and the second
tank (held at ambient temperature, ˜25° C.) collected the
majority of the products. Aqueous phase and heavier hydrocarbon (wax)
products were collected in the 1st tank while an aqueous phase and a
clear liquid hydrocarbon phase was collected in the 2nd tank. The
effluent gas from the 3rd tank was vented. The product gas samples were
collected through a sample port located just downstream from the reactor
and upstream from the first product collection tank and analyzed using an
Agilent M200H micro gas chromatograph with two columns, molecular sieve
5A and PlotQ.

Coolant Side

[0139] A 20 gal (76L) carbon steel tank was used for storing the cooling
water. The water chemistry was maintained with the addition of Cortrol
OS5300 and Optisperse AP302. The tank is pressurized with nitrogen to
maintain the steam loop pressure. Cat Pumps (model 231.3000) were used to
pump the water through the cooling circuit. An Appleton FLSC-62A flow
meter was used to measure and control the coolant flow. The feed water
was passed through a 25 cm, 5-micron particulate filter bank and a 60
micron Swagelok filter prior to entering the reactor. The reactor steam
outlet is connected to a nitrogen source for controlling the coolant
pressure while the water (separated in the coolant footer) flows to a 2
liter stainless steel Swagelok vessel, which was used for maintaining
proper water level in the system.

Performance Data

[0140] The inventive all welded reactor was operated without a
pressure-containment shell for ˜2150 hours. The reactor had an
exoskeleton welded to the exterior to provide the pressure support for
this high pressure reaction.

[0141] The reactor was operated with increasingly severe operating
conditions to the point of thermal runaway (about 70 millisecond contact
time on the process side). After a thermal runaway event, the reactor was
regenerated to evaluate the extent of damage to the catalyst. After
regeneration, the catalyst recovered roughly 50% of initial activity.

Start-Up and Validation Test

[0142] The start-up of the reactor occurred as follows: After completion
of the catalyst activation, the reactor was cooled to ambient temperature
and then pressurized to 350 psig (2413 kPa). Cooling water was the
introduced in the coolant loop at the target flow rates and the reactor
was heated to the syngas introduction temperature of ˜170°
C. Syngas flow was then started in steps and the reactor heated to the
target operating temperature.

[0143] Upon completion of the start-up, the reactor attained the condition
of H2:CO=2.0, P=350 psig (2413 kPa), diluent ˜16.8%, CT
˜290 ms. Two rows of thermocouples were tack welded on the external
reactor surface at approximately 1.17 cm (0.46 in) and 3.2 cm (1.26 in)
from the start of the catalyst bed (3.20 cm and 5.23 cm from the reactor
inlet). The inventive all welded microchannel reactor did not create a
fully isothermal reactor operation; however, the measured temperature
gradients were less than about 5° C. Further, the internal
gradients on the FT catalyst were not measured and are expected to be
greater than the measured thermal gradients measured in the reactor
walls.

The temperature profile across the face of the reactor was controlled to
within ±2° C. of the average temperature.

[0144] A direct comparison of the inventive (all welded) reactor
performance to the brazed reactor is tabulated below in Table 1 based on
the same Fischer Tropsch catalyst:

[0145] Time on stream performance of the inventive all welded reactor is
comparable to the other brazed and single channel reactors at the same
conditions.

The product wax collected during this validation period was analyzed for
the carbon number distribution. The results showed an excellent agreement
with the wax from earlier tests at similar conditions with short and long
single channel reactors and brazed pilot-scale reactor tests.

Robustness to Process Upsets

[0146] At approximately 211 hours on stream, a coolant flow meter failure
led to an interlock incident. The coolant flow meter failure triggered a
zero flow alarm (despite the pump functioning normally) causing the
back-up pump to start resulting in a significantly higher coolant flow
which led to an interlock. Within 5 minutes the system was reset. The
reactor had cooled to ˜197° C. during that period. The CO
and H2 flows were immediately turned ON once the system was reset.
The N2 flow was turned ON 2 minutes later. The reactor temperature
started to increase immediately and within 9 minutes (from system reset)
the maximum temperature recorded on the reactor external surface reached
˜240 C as there was no coolant flow (since the coolant channels
were not drained, a pool of water from prior operation would be there on
the coolant side which may have started to vaporize). As the temperature
reached 240° C. (9 minutes from system reset), the coolant pumps
were started manually. The reactor temperature started to drop back to
normal levels. Within 28 minutes (37 minutes from the system reset) the
situation was under control and the reactor had cooled to ˜192 C.
The reactor temperature was then gradually increased to the value prior
to the interlock (˜206.6 C). Upon reset, H2 flow was set to a
higher value than the target resulting in a H2:CO ratio of 2.17 (instead
of 2.00).

[0147] This experimental result was surprising in that thermal runaway did
not occur within seconds of losing the coolant feed and that 9 minutes
passed between the loss of coolant and the reactor temperature rising
more than 40° C. The catalyst performance was brought back to
expected levels after restarting the coolant and achieving the target
temperature. The high ratio of metal reactor block volume to catalyst
volume creates a thermal sink to absorb the exothermic heat of reaction
for a few minutes while system upsets are reversed. This is particularly
advantageous over conventional tubular fixed bed FT reactors whereby
temporary loss of coolant results in a thermal runaway event and loss of
catalyst performance. The inventive FT reactor creates a modest temporal
buffer for undesired thermal upsets as shown for the return to expected
performance after 9 minutes without coolant flow. The reactor temperature
rose as expected, but the high heat capacity of the metallic structure
kept the catalyst from permanently sintering.

[0148] For the all-welded pilot reactor, the catalyst volume was ˜7%
of the total reactor volume (63.1 ml catalyst in 0.934 L reactor block
-10''×3''×1.9'' (25 cm×7.5 cm×4.75 cm)). For this
ratio of reactor volume to catalyst volume of ˜14:1 the thermal
sink time of 9 minutes without coolant was shown to be acceptable.

[0149] For larger devices where the ratio of reactor volume to catalyst
volume is less than 14:1 and more typically less than 10:1, and more
preferably still less than 3:1 or 2:1, the acceptable time without
coolant flow will be less than 9 minutes, and is expected be 5 minutes or
less, in some embodiments, 30 seconds or less. In some preferred
embodiments, the ratio of catalyst volume to reactor volume is between 2
and 60%, in some embodiments of reactors according to the present
invention, between 5% and 40%; where total reactor volume includes the
volume of channels, channel walls, integrated manifolds and exterior
walls, but not exterior piping or pressure containment vessels.

[0150] Additionally, at ˜346 hours on stream, a carbon monoxide mass
flow controller was changed out due to a low dry test meter (DTM) reading
for the outlet flow. The new CO MFC was set to a value lower than target
resulting in an increased H2:CO ratio. During the subsequent period of 17
hours (up to ˜363 hours on stream), the H2:CO ratio was ˜2.36
and the CO conversion increased to a value >85%.

[0151] Surprisingly, we discovered that even at high CO conversion the
rate of deactivation did not increase and performance was restored to
previous levels after adjusting the feed ratio. The reactor has robust
operation to a varying range of conditions, including a higher level of
H2 to CO. Conventional tubular fixed bed FT reactors do not respond well
to quick changes in the thermal output, including a sudden increase in
the released heat from the reaction. The inventive reactor continued to
operate in a stable fashion as the heat of reaction increased with a
higher H2 to CO ratio. Further the performance went back to the expected
performance after the syn gas ratio was restored to the target value.

Partial Boiling Evaluation Run

[0152] In the next phase of inventive reactor demonstration, partial
boiling of coolant was tested and validated the thermal control and
stability of the inventive all-welded reactor which only sealed the
boiling flow control features (22 wavy turns of the smaller cross
sectional channel at the inlet side before the main coolant channels)
along a linear seam between the parallel wavy features rather than
following the contours of the wavy features. There is one wavy feature
section per coolant flow channel, and the simple linear seal between
parallel coolant channels was sufficient to maintain stable operation in
a high heat flux partial boiling controlled reaction, e.g. flow did not
appear to bypass the turns along the lands adjacent to the serpentine
features which would thereby lower the upfront pressure drop and
potentially lead to coolant flow destabilization during boiling.

[0153] Operating conditions corresponding to the "home" condition
(H2:CO=2.0, P=350 psig (2413 kPa), diluent ˜16.8%, CT
˜290 ms) were maintained. Starting at ˜634 hours on stream,
the coolant flow was lowered from ˜2 LPM such that an outlet steam
quality of ˜1-3% boiling was achieved. The reactor temperature was
also adjusted to maintain ˜70% CO conversion. At ˜679 hours
on stream, the coolant water flow rate was decreased to 0.4 LPM and an
exit steam quality of 1.5% was attained. The reactor temperature was
lowered to 204.3° C. to maintain the target CO conversion. The
performance is substantially similar to the single phase operation.
Further, the use of partial boiling allows the reactor to be operated
with higher net heat flux or heat generation from an FT reactor operated
with lower contact time than the initial 290 ms.

[0154] The partial boiling conditions were held for ˜300 hours on
stream and the performance during this period is summarized in FIG. 10.

The inventive reactor operated stably for >250 hours on stream with
partial boiling of water and an exit steam quality of 1.5% at the "home"
condition of 290 ms to substantially match the performance of the single
phase coolant.

Thermal Stability Evaluation Run

[0155] In the next phase of testing, the ability of the inventive reactor
to effectively remove heat was tested by increasing the heat duty of the
reaction (processing more syngas by lowering contact time while maintain
CO conversion by adjusting temperature). It is noted that the process
fins were only press fit in contact with the coolant subassembly. The
contact resistance of a press fit process fin with a coolant subassembly
did not substantially change the performance of the exothermic FT
reactor. Further, the press fit of the fins against one wall was hindered
by a raised rib or nub on the order of 0.013 to 0.13 mm (0.5 to 5 mils)
high and 0.025 to 0.508 mm (1 to 20 mils) wide arising from the laser
welding method of manufacturing the subassembly.

[0156] While maintaining the 16.5% dilution, H2:CO=2, and an operating
pressure of 350 psig (2413 kPa), the process reaction contact time was
reduced in steps from 290 ms to ˜70 ms.) For example, given the
66.5 grams of catalyst and 63.1 cm3 volume of the catalyst bed, a
change from 290 ms (13.1 SLPM flow) to 70 ms increases the syngas flow to
the reactor to 54.1 SLPM. The composition of the syngas and the details
of the transition are presented in table 2 below. The temperature was
increased from 206.6° C. to ˜263° C. to maintain
˜70% CO conversion. As a result of this higher heat duty--the
ability of coolant to remove heat was tested. The key data during this
phase of operation is shown in table 2 below:

Based on the above data, the inventive welded reactor design can handle
more than four times the heat load than that produced at the 290
millisecond contact time condition (with the average steam quality
increasing from ˜1.5% to ˜10%). The individual phases of
operation and comparison to similar test conditions from tests with other
devices (brazed and single channel reactors) are presented below:

[0157] The inventive welded reactor was tested at a contact time of 210 ms
from 945 to 1131 hours on stream. Other process parameters were held
constant at H2:CO=2.0, P=350 psig, (2413 kPa) diluent ˜16.5%.
The reactor temperature was increased to 214.6° C. to maintain
target CO conversion.

[0158] The inventive welded reactor was tested at a contact time of 150 ms
from 1132 to 1182 hours on stream. Other process parameters were held
constant at H2:CO=2.0, P=350 psig, (2413 kPa) diluent ˜16.5%.
The reactor temperature was increased to ˜221.7° C. to
maintain target CO conversion.

[0159] The inventive reactor was tested at a contact time of 100 ms from
1205 to 1350 hours on stream. Other process parameters were held constant
at H2:CO=2.0, P=350 psig, (2413 kPa) diluent ˜16.5%. The
reactor temperature was increased to ˜241.2° C. to maintain
target CO conversion. During a period of ˜1221-1228 hours on
stream, the CO mass flow controller failed due to a water drip causing an
interlock incident and had to be replaced.

[0160] The contact time was then lowered more gradually in steps of 5 ms
from 100 ms to 70 ms. Other process parameters were held constant at
H2:CO=2.0, P=350 psig, (2413 kPa) diluent ˜16.5%. At a contact
time of 70 ms and a reactor temperature of ˜263.1° C.
(˜1542 hours on stream) unsteady run-away behavior was noted at
multiple thermocouple locations on the reactor. A sudden rapid increase
in the temperature is seen at constant conditions (prior to the run-away
being controlled by lowering the reactor temperature) as indicated in the
graph in FIG. 11.

[0161] The temperature described in FIG. 22 is measured in on the external
metal wall of the reactor which is on the opposite surface of the 1.27 cm
(0.5 in) thick support plate that is in contact with the outermost
coolant channel. The metal temperature rise is less than 10° C.
but indicative of a temperature rise on the catalyst bed estimated to be
greater than 50° C.

[0162] During this period of operation, the higher capacity of the
inventive welded reactor was also demonstrated. The wax material from the
290 ms, 210 ms and 150 ms contact time operation was analyzed to
calculate the alpha number. The device performance is summarized below in
Table 3:

[0163] In this part of the study from 1662 hours on stream to 1783 hours
on stream, the coolant flow was lowered from 0.5 LPM (keeping other
operational parameters constant at H2:CO=2, 16.5% dilution, 350 psig
(2413 kPa) process pressure) to increase the extent of boiling at the
same heat duty and achieve higher exit steam quality. At ˜1712
hours on stream, at 0.2 LPM of flow, the flow meter reached its lower
limit of reading and the water flow rate could not be lowered any
further. The average steam quality during this phase of the test
increased to ˜15% as illustrated in the table 4 below:

[0164] During the operation of the FT reactor the laser welded subassembly
moves from compression to tension on the subassembly as the fluid
pressure inside the coolant subassembly increases with time on stream.
Specifically, the section of the coolant subassembly that is adjacent to
process layers is smaller than the entire coolant subassembly. For the
all welded reactor described in this example, roughly 60% of the
subassembly is adjacent to the finned process layer and will undergo
changes in compression and tension. A larger reactor with a
24''×24'' (60 cm×60 cm) subassembly will have more than 80%
of the subassembly surface area transitioning between compression and
tension as the boiling temperature is changes with the pressure. The
reaction temperature is typically increased for a Fischer Tropsch
reaction as the catalyst deactivates with the buildup of wax. A typical
starting temperature is between 200° C. and 210° C. where
the boiling temperature from the steam curve is roughly between 210 and
260 psig (1448 and 1793 kPa). The process feed pressure is typically
between 250 psig and 450 psig (1724 and 3101 kPa). The temperature is
raised by increasing the pressure on the coolant side. At 220° C.,
the steam pressure during boiling (the preferred method for removing the
exothermic heat of reaction for Fischer Tropsch) is roughly 320 psig
(2206 kPa). At 230° C., the steam pressure is roughly 380 psig
(2620 kPa). For the experiments described in this example, the process
temperature was raised to above 250° C., where the steam pressure
is roughly 560 psig (3861 kPa) and significantly above the process
reaction pressure. At the start of run, the laser welds were in
compression from the higher pressure on the fin or process side. At the
highest temperature, the laser welds were in compression and were as high
as 332 psig (2289 kPa) greater pressure on the coolant side than the
process side. Before and after regeneration, the reaction temperature was
dropped to below 220° C. and the laser welds were returned to
compression rather than placed in tension. The laser welded subassembly
was robust to operating in both compression and tension and back to
compression within a time span of more than 1000 hours time on stream.
Further, not only were the laser welds robust to operating in either
compression or tension and back again, but the thermal contact of the fin
and catalyst compaction was not affected by pressure changes within the
device. An important parameter for maintaining good performance of this
inventive reactor is a well loaded catalyst bed, preferably where the
catalyst load density is within 2% and preferentially 1% of the
theoretical PABD (packed average bed density) as determined externally by
ASTM methods for a particulate material. A cold flow pressure drop test
may be used to compare actual pressure drop versus that predicted from
the Ergun equation. If the pressure drop is not within 5% (with 2%
preferred) of predicted from the Ergun equation then the bed is poorly
packed. If the bed is poorly packed, there will likely be deleterious
effects of flow channeling in the reactor and the change between
compression and tension with respect to the process and coolant channels
may lead to an increase of unwanted forces on catalyst particles such
that attrition or grinding could occur. If the catalyst particles were to
break apart, then the resultant small particles would likely lead to a
higher pressure drop in some channels over others and could lead to flow
maldistribution, hot spots, or premature thermal runaway.

[0165] To summarize, the performance of the all welded reactor was
validated and demonstrated that brazing and/or diffusion bonding are not
required. The thermal contact enabled by the all-welded manufacturing
technique provided desirable results.

[0166] The initial coolant pressure over process pressure was limited to
˜50 psi (345 kPa) to prevent the popping of the welds between the
coolant channels and deformation of the waveforms based on the size of
the laser welds for this inventive reactor and burst testing of similar
sized laser welded parts. During the run, this overpressure was increased
to ˜332 psi (2289 kPa) and no externally visible deformation was
noted. After testing, a reactor autopsy confirmed that no reactor
internals were compressed or deformed or otherwise undesirably changed.
This surprising result suggests that the catalyst loaded fins provided
structural support for these small laser welds, which were 0.002 inches
(0.005 cm) wide. Laser welds on can be made wider, for example, 0.006
inch (0.0150 cm) or greater to allow for a full high pressure operation
on the coolant without requiring support from the catalyst loaded process
channel. Thus, in preferred embodiments, apparatus and methods according
to the invention use laser welds having a width of 0.015 cm or greater.

Example 3

Large Sheet Laser Welds

[0167] Three types of parts were tested for the inventive reactor to show
the impact of dissimilar part thickness for the laser welded
subassemblies. It was originally theorized that thinner top sheets would
create less distortion because the energy input to form the weld was
lower. Surprisingly, it was found that the thinner top sheets gave more
distortion rather than less. The thicker top sheets were preferred.
[0168] Top sheet welded to a coolant channel shim ranged from 0.020''
(0.05 cm) Wall, 0.010'' (0.025 cm) Wall, and a 0.005'' (0.025 cm) (0.125
cm) Wall [0169] Initial welding was conducted with intermittent laser
welds to help fixture the parts. (e.g every fifth Row). Before the long
seam weld lines were made, intermittent laser welds along the weld length
dimension were added in every fifth row. The intermittent stitching was
roughly 2 to 4 cm long and separated by un-welded sections of 5 to 20 cm
in length [0170] The Top plate was then removed and Full Length Welding
was performed [0171] Power setting and focus needed to be adjusted for
the two thinner wall scenarios [0172] 60% power setting for the 0.010''
(0.025 cm) Wall [0173] 50% power setting for the 0.005'' (0.0125 cm) Wall

[0174] The initial thought was the distortion would be less as the wall
thickness and power were reduced, however the opposite occurred. The
0.020'' (0.05 cm) Wall Subassembly was measured and showed ˜2.750''
(6.875 cm) distortion.

[0178] In the tested assemblies, there were over 161 24'' (60 cm) long
welds along the 24'' (60 cm) width of the assembly and the stresses seen
in these components are not a surprise, but are the longitudinal and
transitional stresses normally seen when performing long welds. The
challenge is to mitigate the stresses during the weld process or to
reduce/remove the stresses after the subassembly process.

[0179] Preferably, individual top sheets have a thickness of 0.04 cm or
greater, in some embodiments, in the range of 0.04 cm to 0.2 cm; more
preferably, 0.05 cm to 0.1 cm. "Top sheet" refers to the sheet that is
placed over a sheet or multiple sheets that contain channels or other
voids; the top sheet seals the channels or voids in the height direction
and completes a subassembly.

Pre Cambering Test for Large Parts

[0180] One method for mitigating the stresses of welding was by means of
pre-cambering (pre-bending) components then performing the operation was
tried out. The following process was used:

[0187] Pre-cambered components were made by using fixturing that consists
of clamps and tie down straps to allow for a controlled and consistent
flex of the components (see FIG. 12). The sheets were bent in the
direction perpendicular to channel length. Two sheets were pre-cambered
with this technique and then welded. The resulting subassembly was
visually compared to a subassembly made similarly but without
pre-cambering. [0188] Stress relieving at temperatures below
400° C. is an acceptable practice but results in only modest
stress relief. One hour at 870° C. typically relieves about 85% of
the residual stresses. However, stress relieving in this temperature
range can also precipitate grain boundary carbides, resulting in
sensitisation that severely impairs corrosion resistance in many media.
To avoid these effects, it is recommended that a stabilised stainless
steel (grade 321 or 347) or an extra-low-carbon type (304L or 316L) be
used, particularly when lengthy stress relieving is required. Stress
relieving the large part was tried at 400 C and at a higher temperature,
1100 C. For both cases, limited success was noted. A modest reduction in
deformation was observed, 40% of the original warpage as measured by the
distance one edge lies above flat. [0189] Annealing (often referred to as
solution treatment) not only recrystallises the work hardened grains but
also takes chromium carbides (precipitated at grain boundaries in
sensitised steels) back into solution in the austenite. The treatment
also homogenises dendritic weld metal structures, and relieves all
remnant stresses from cold working. Annealing temperatures usually are
above 1040° C., although some types may be annealed at closely
controlled temperatures as low as 1010° C. when fine grain size is
important. Time at temperature is often kept short to hold surface
scaling to a minimum or to control grain growth, which can lead to
"orange peel" in forming.

Example 4

Fin Impact in Welded Reactors

[0190] Waveforms comprising press-fit fins with high aspect ratios are
likely to not be straight, but have some bow or bend to the fins. After
compressing into contact with two solid strips on either side of the
fins, the fins bend or bow even more. In the inventive welded reactor,
the fins are pressed to the adjacent surfaces, rather than brazed or
bonded, resulting in more contact resistance or thermal resistance at the
point contact of the fins with the adjacent surfaces. In exothermic or
endothermic reactions, the heat of reaction is transferred between the
fins and the adjacent surfaces. To improve thermal contact with a press
fit, the fins are taller than the supporting edge strips. As the fins are
compressed into contact by an external load, they bend or buckle. As the
fins bend, they are less likely to retain inherent strength.

[0191] Press fit fins of 0.006'' (0.015 cm) thick Cu110, 0.256'' (0.64 cm)
high compressed against edge strips that are 0.25'' (0.63 cm) high. The
fins become more eccentric as they are pressed against the adjacent heat
transfer walls. In the photograph in FIG. 13, the horizontal lines can be
seen where the fins sit on top of the laser weld lines that seal the
cross flow heat exchange channels.

[0192] The press fit reactor described in Example 1 performed surprisingly
well, matching the performance of the brazed reactor which did not have
the laser welding ridges separating the fin from the heat transfer wall
resulting from a combination of the high thermal conductivity of the
copper fin conducting more heat to the heat transfer wall--including
aided by axial conduction to better points of thermal contact, and or the
filling of the small gap (estimate between 5 and 150 microns) with
hydrogen and or Fischer Tropsch liquids produced during the reaction. The
thermal conductivity of hydrogen and the liquid oil is substantially
higher than most gases and thus will reduce the impact of a poor contact
resistance between the press fit fin and the heat transfer wall. Further,
the advantageous use of copper with a very high thermal conductivity
enables efficient axial conduction to move heat to the heat transfer
interface without building up a hot spot and creating or exacerbating
unwanted side reactions.

[0193] A load of 2600 psi (17,926 kPa) was applied to the stack to bring
the stack into contact. A preferred range of loads may be from 500 psi
(3447 kPa) to 500,000 psi (3,447,000 kPa) depending upon the height of
fin, the fin material, the fin thickness, and the eccentricity of the
starting fin. After compression and the first TIG welding along the side
bars or edge strips is complete, the fin contact is made with the heat
transfer subassembly.

Example 5

Large Laser Welded Subassembly Linear Density of Weld Per Unit Area of
Subassembly

[0194] This example describes a 24''×24'' (60 cm×60 cm) laser
welded subassembly with laser weld lines running along the 0.6 m length
with the direction of coolant flow. There were 161 coolant channels on
this panel and 162 laser weld lines to seal the device between the
coolant channels and provide structural support to prevent deformation of
the equipment during operation at pressure.

[0195] For this sample, there is 97.2 m of linear weld in a 0.6
m×0.6 m part or a linear weld density of 270-m per m2 of surface
area. Alternatively, the linear density could be described as 2.7 cm/cm2
in a 3600 cm2 size part for this embodiment. For other embodiments, the
linear density of welds could be greater than or less than 2.7 cm/cm2
and, in preferred embodiments, may range from 0.1 cm/cm2 to 10 cm/cm2.

Example 6

Laser Weld Registration

[0196] FIG. 14 shows laser weld lines that join the top of the ribs
between parallel and adjacent coolant channels formed in the bottom
plate. The laser weld joins the bottom channel plate to the top plate.
The laser weld may be applied along the tops of the ribs that are formed
in the bottom or channel plate. In this example, the rib is 0.037''
(0.093 cm) wide and the laser weld width may vary from 0.002'' (0.005 cm)
to 0.01'' (0.025 cm) wide. The laser weld may be in the middle of the
rib, or to either side or anywhere along the width of the rib.

Example 7

Manufacturing a Large FT Reactor

[0197] The all welded Fischer-Tropsch reactor core is built primarily as
dual layer assembly of alternating coolant and process portions. A
feature to this design is that a coolant sub-assembly is welded in such a
way that it maintains mechanical integrity as a standalone unit. One
process of creating such a sub-assembly is by using laser welding to join
a top solid shim to a featured shim by placing welds between each
channel, running parallel to the ribs. It has been demonstrated that the
required mechanical integrity can be obtained with such an approach. A
second parameter that must be addressed is that of part flatness. Welding
two thin sheets in such a manner can cause considerable sub-assembly
deformation due to the material shrinkage associated with welding
stainless steel. Sub-assembly deformation can lead to added complexity
and effort required to either re-flatten the pieces or adapt the stacking
process the handle the deformed pieces.

[0198] One method that has been found to minimize the distortion due to
welding is to limit the overall size of the sub-assembly. It has been
found that by using a subassembly that incorporates 24'' (60 cm) long
welds between channels but which is limited to approximately 6'' (15 cm)
in width maintains an acceptable level of flatness whereas a similar
assembly that is includes a width of 24'' (60 cm) does not (e.g. overall
part is 6''×24'' vs 24''×24'', (15 cm×60 cm vs 60
cm×60 cm)). Furthermore, multiple of these 6'' (15 cm) wide
sub-assemblies can be stitch welded together and maintain reasonable
flatness. In this manner, a 24''×24'' (60 cm×60 cm) flat
subassembly can be built by stitch welding four 6''×24'' (15
cm×60 cm) subassemblies together which is substantially flatter
than a 24''×24'' (60 cm×60 cm) subassembly welded from
starting 24''×24'' (60 cm×60 cm) parts.

[0199] Another useful feature which can be built into the welded
sub-assembly is one which will allow the pieces to be accurately checked
for leakage and mechanical integrity prior to using them to build the
entire FTR welded stack. This can be accomplished by slightly oversizing
the initial sub-assemblies, adding a port through which pressure can be
applied, and initially sealing the ends of the sub-assemblies as part of
the laser welding process. This pressure test can be hydrostatic or
pneumatic. After the individual pieces have been welded and qualified the
assemblies go through a trimming step that cuts them to the correct
6''×24'' (15 cm×60 cm) size and which opens the flow ends of
the channels followed by stitch welding four 6'' (15 cm) subassemblies
together to form one 24''×24'' (60 cm×60 cm) coolant
subassembly.

[0200] The final subassemblies are then interleaved between process layers
to form the main reactor core. The stacking process consists of first
putting down a 2'' (5 cm) thick clamp plate, followed by a 1'' (2.5 cm)
thick endplate and then proceeding with the alternating coolant and
process layers. The stacking ends by placing a final coolant subassembly,
followed by a top end plate and top clamp plate. Pressure is applied to
the stack to pre-compress the copper waveforms while bringing all
components into metal to metal contact. The applied pressure may range
from 20 psi (138 kPa) to 500,000 psi (3447000 kPa), with a preferred
range of 20 to 20,000 psi (138 kPa to 138000 kPa) and a more preferred
range of 20 psi to 5,000 psi (138 kPa to 34474 kPa). The stack is then
secured into place using a clamping system prior to releasing the applied
pressure. The clamping system maintains the stack in this compressed
state so that the core welding can take place.

[0201] The core welding consists primarily of three steps: adding strength
welds two both process faces, adding seal welds to both coolant faces,
and adding two endplate sealing welds on each process face to prevent
bypass. The reactor remains in the clamp state during each of these
welding steps to ensure the best thermal contact possible within the
core. Note that each of the three core welding steps serves a unique
purpose. The strength welds that occur on the process faces are applied
first and give the overall stack enough mechanical strength that the core
can be easily manipulated (lifted, rotated, or otherwise oriented) during
the other two weld steps as well as all subsequent fabrication steps. The
seal welds that occur to the two coolant faces are the primary welds that
guard against internal cross leaks (process to coolant or vice versa)
within the reactor. The endplate seal welds are used to seal the
outermost coolant subassemblies to the top and bottom endplates. Although
these are sealed on the coolant faces to avoid cross leakage, they must
also be sealed on the process faces to avoid process gas flow moving
between these parts and thus bypassing the catalyst bed. It is noted that
the catalyst is loaded into the reactor and in between the process fins
after final assembly.

[0202] Before the core is welded into an assembly, the reactor should be
substantially leak free. The welded reactor has not yet been prepared to
withstand any significant internal pressure, so a bolt on clamping
mechanism can be used to provide support. Once the reactor core is
qualified it proceeds to have the coolant header welded in place. Once
this step is done the reactor can go through coolant side flow testing if
desired or warranted. The corresponding coolant footer is then welded in
place. Both coolant manifolds are suited for operation and provide part
of the foundation of the external support system of the reactor.

[0203] Since, with the exception of the coolant subassemblies, all welding
has been done to the perimeter of the core the reactor cannot withstand a
significant internal process pressure without deflecting out the top and
bottom endplates due to the pressure induced load and hence the reactor
cannot achieve operating conditions in its current state. In order to
give the reactor mechanical integrity, a system (an exoskeleton) of
external supports are welded around the reactor core. These supports are
designed to counterbalance the internal process pressure and thus control
any pressure induced deflection of the top and bottom plates to an
acceptable level. The external supports act as stiffeners welded across
both top and bottom endplates of the reactor and which are then joined
from top to bottom. They counter balance any loads created by internal
pressurization and hence prevent any deformation that might otherwise
occur. They are less thick than tall with multiple sets spanning across
the reactor (see FIG. 15). Preferably, each stiffening element is at
least 3 times, more preferably at least 5 times taller than thick (taller
refers to height in the stacking direction). In some embodiments, the
spacing between sets of supports, as well as their thickness and height
are determined based on the process loads to be balanced. In one example,
the supports are created from 0.75 inch thick stainless steel plate
extending approximately 8'' high across the top and bottom endplates with
approximately 3'' spacing between them. As a final qualification step,
the core can have temporary manifolds welded onto the process faces and
undergo high pressure testing to confirm the reactor has met the design
criteria. After this step the process manifolds are removed and the core
can be prepped for catalyst loading, after which the final process
manifolds are welded in place.

[0204]FIG. 16 illustrates an example in which four 6''×24'' (15
cm×60 cm) sub-assemblies are placed side by side and welded in
several locations to join into a 24''×24'' (60×60 cm)
assembly. Spot welding is preferred to join subassemblies in this manner
because continuous welds were found to lead to more deformation.

Example 8

[0205] The device of example 8 is a welded reactor or device which
provides for cross-flow heat transfer between two fluid streams.
Alternate flow configurations could be used, but the specific described
example is cross flow. External supports were welded in an array (see
FIG. 17) to the outside of the device core to allow pressurization of
internal passageways in the device relative to a low pressure external
environment without compromising device integrity or losing containment.
The "exoskeleton" or array of external supports enables the device to
withstand high pressure differentials to the external environment. The
device was constructed of 304L stainless steel, including the external
supports. The use of an exoskeleton allows for the operation of a welded
reactor for Fischer Tropsch reactions and other reactions or heat
exchange applications or high pressure operations without the use of an
external pressure vessel. The devices are in tension rather than in
compression as present with an external pressure vessel with a higher
pressure fluid surrounding the inventive reactor or device.

[0206] The 61 cm by 61 cm by ˜6.5 cm device core of Example 8 was
made up of layers which are welded around the perimeter, as described in
the attached application. The external supports were 1.9 cm thick by 105
cm long, with a width of about 14 cm near the ends and about 17 cm in the
region adjacent the 61 cm by 61 cm face. The supports were spaced 10.2 cm
apart (center to center), with 1.9 cm thick cross-members placed between
the supports along each end of the device (so that the two rows of cross
members are about 60 cm apart). The weldments between external supports
and cross members were full penetration bevel welds.

[0207] A hydrostatic test was first performed on a process stream flow
circuit. The procedure used (shown graphically in FIG. 18) was as
follows: [0208] 1. Determine the baseline leak rate during pressure
test with nitrogen at about 690 kPa (psig). [0209] 2. Fill the device
with water using a pump (in this Example a Lab Alliance HPLC "Prep Pump"
was used). [0210] 3. Use the pump to raise the pressure from ambient
pressure (i.e. <450 kPa) to ˜3300 kPa (464 psig) at a rate of
˜300-400 kPa/minute. [0211] 4. Drop the pressure at a rate of
˜50-100 kPa/min to below ˜3000 kPa (420 psig). [0212] 5. Use
the pump to raise the pressure from ˜3000 kPa (420 psig) to
˜3700 kPa (522 psig) at a rate of ˜50-100 kPa/minute. [0213]
6. Use the pump to raise the pressure from ˜3700 kPa to >6000
kPa (855 psig) at a rate of ˜100-150 kPa/minute. [0214] 7. Drop the
pressure at a rate of ˜250-300 kPa/min to below 5300 kPa (754
psig). [0215] 8. Continue to drop the pressure until ambient conditions
are reached and drain the water from the device. [0216] 9. Repeat Step 1.
A second hydrostatic test was then performed on the coolant stream flow
circuit. The procedure used (shown graphically in FIG. 19) was as
follows: [0217] 10. Fill the device with water using a pump (in this
Example a Lab Alliance HPLC "Prep Pump" was used). [0218] 11. Use the
pump to raise the pressure from ambient pressure (i.e. <250 kPa) to
˜3500 kPa (495 psig) at a rate of ˜2000-2500 kPa/minute.
[0219] 12. Use the pump to raise the pressure from ˜3500 kPa to
>6000 kPa (855 psig) at a rate of ˜800-900 kPa/minute. [0220]
13. Drop the pressure at a rate of ˜400 kPa/min to below 5200 kPa
(740 psig). [0221] 14. Continue to drop the pressure until ambient
conditions are reached and drain the water from the device. [0222] 15.
Re-check the leak rate at about 690 kPa (100 psig) and compare with the
baseline pressure test leak rate.

[0223] Hydrostatic testing of the coolant and process circuits was
performed using the above protocols. The device showed no indication of
mechanical failure during hydrostatic testing. The leak rates from
coolant circuit to process circuit before and after this hydrostatic
testing measured as drop in pressure over 15 minutes time with 690 kPa
(100 psig) initial pressure in the coolant circuit were 0.6 kPa (0.09
psi) and 21 kPa (3.05 psi), respectively. The device was then repaired
via welding and the leak rate from coolant to process circuit was
measured as 2.2 kPa (0.32 psi) drop in pressure over 15 minutes time with
690 kPa (100 psig) initial pressure. Repair welding was conducted using a
fiber laser. Alternatively, TIG, MIG, or other conventional methods of
welding could be used.

[0224] The welded reactor core was assembled from laser welded coolant
subassemblies and welded into a final reactor. The reactor as then
subsequently contained with an exoskeleton which permits high pressure
service. For the Fischer Tropsch reactor, the hydrostatic pressure test
is 855 psig (5895 kPa). Alternatively, a higher or lower hydrostatic
pressure test could be used for Fischer Tropsch service depending on the
final desired operating conditions. The described hydrostatic test in
this example qualifies a reactor for service at a peak design temperature
of 250 C and a peak design pressure of 562 psig (3875 kPa). The operating
temperature and pressure would be lower than the peak design pressure to
allow a margin of operating safety. For a desired higher operating
pressure for a Fischer Tropsch reactor the spacing of external supports
as shown in FIG. 17 would be decreased and additional supports added to
qualify the reactor for a higher operating pressure.

[0225] Other reactions when operated at a higher temperature or pressure
would be enabled by the inventive exoskeleton but may require additional
supports which are more densely spaced. Alternatively, if a required
process design pressure or temperature were lower, then a more sparsely
populated welded support bars would be used. The inventive welded reactor
can be operated at high temperature and high pressure without being
disposed within a pressure containment vessel or without having a brazed
or bonded reactor core.

[0226] The inventive exoskeleton allows for a reactor or device to pass a
hydrostatic test whereby at a high internal pressure and a low external
pressure the reactor retains mechanical integrity and is fit for service.

Example 9

Leak Test

All-Welded Device Leak Check Test

Summary

[0227] The all-welded FT devices were leak checked pneumatically up to and
including 100 psig (690 kPa) on both the process and coolant sides,
independently. In some embodiments, the leak check pressure may be as
high as 200 psig (1380 kPa), or 500 psig (3450 kPa), and in one
embodiment as high as 1000 psig (6900 kPa). Pressure drop over time is
recorded to determine if the device leaks and interfaces are Snooped
(leak-tested) to identify location of any leaks. To enable pressurization
of either side, gasketed headers and footers are secured to the device
via an all-thread clamping setup. The device is pressurized in increments
of 10-20 psig (90-180 kPa), stopping after each increment to check the
pressure drop rate, check the gaskets and all fittings for leaks and
identify any leaks within the device.

Example 10

Ultra-Tall Fins Enabled by Inventive Reactor for Fischer Tropsch and Other
Chemistries

[0228] The all welded reactor where process layers (including fin
structures) are placed adjacent to coolant subassemblies to form a final
device assembly enables the use of unconventional process layers,
including those with ultra tall fins. Ultra tall fins would create
problems during brazing or bonding as they would provide little if any
structural support during the bonding or brazing process and as such
would sag, deform, or otherwise have a resultant structure that would
require fixing or straightening prior to use--if even possible to do so.
Excessive deformation from an ultra tall fin (such as about 0.5 in or
1.25 cm or greater) after brazing or bonding would render the device
unusable.

Case A: Fin Height 0.225'' (0.5625 cm)

[0229] A Fisher-Tropsch reaction is conducted in a microchannel reactor.
The microchannel reactor contains a number of parallel process channels
packed with FT catalyst. The reaction heat is removed by the coolant
channels between the process channels where the water is the coolant. The
removal of the reaction heat generated inside the catalyst bed is
enhanced by the imbedded fin structure. The continuous fin inside the
process channel, forms a series parallel flow paths. In this example, the
fin is made of copper 110. The process channel height is 0.225'' (0.5625
cm) and the length is 23'' (57.5 cm). The fin has the same length and the
spacing between the adjacent fin ribs is 0.04'' (0.1 cm) and the fin
thickness is 0.006'' (0.015 cm). It is assumed there is no contact
resistance between the fin and the process channel walls. The process
channel wall thickness is 0.02'' (0.05 cm) and made of stainless steel.

[0230] The process channel contains a certain amount of Co catalyst and is
described in the first example. The void fraction of the catalyst bed is
roughly 0.4 and the effective thermal conductivity is roughly 0.3 W/m-K.
The catalyst loading is 1060 kg/m3.

[0231] The complex FT reactions are modeled as a simplified reaction
network with 6 volumetric reactions (See Table 5). The parameters (Table
6) in the rate expressions are regressed using the catalyst test data in
a lab scale FT reactor.

Here are the operating conditions used in the FT reactor models, [0232]
Temperature on the process channel walls: 230 C [0233] Pressure at the
beginning of the catalyst bed: 412 psig (2840 kPa) [0234] H2/CO ratio in
the feed: 2.1. [0235] Nitrogen dilution in the feed: 31.3% (vol.) [0236]
The process feed is preheated to the same temperature as on the channel
walls. [0237] The feed flowrate over one unit catalyst packing of 0.04''
(0.1 cm)×0.225'' (0.563 cm)×23'' (57.5 cm): 1197 SCCM. The
contact time calculated based on the catalyst volume is 0.17 second. The
predicted catalyst bed temperature as a function of the reactor length is
shown in FIG. 20. The temperatures are sampled along the center of the
catalyst bed so that the peak of the curve represents the maximum
temperature of the catalyst bed. In this case, it is 239 C and located a
short distance from the beginning of the catalyst bed. The CO conversion
is projected at 76.0% and methane selectivity is at 15.3%

[0238] Case B: Fin Height 0.5'' (1.25 cm)

[0239] A Fisher-Tropsch reaction is conducted in a microchannel reactor.
The reactor configuration is similar to the reactor in Case A. The only
difference is the process channel and the copper fin heights are 0.5''
(1.25 cm). It would be expected that for a nominal 0.5'' (1.25 cm) fin
height, that the starting fin height would range between 0.501'' (1.253
cm) and 0.052'' (0.13 cm), with a preferred range of 0.504'' (1.26 cm) to
0.510'' (1.275 cm) placed next to nominal 0.5'' (1.25 cm) high side bars
or edge strips or p-strips.

[0240] In this example, operating conditions are the same, except the feed
flowrate which is scaled up according to the total catalyst loading
volume to keep the same reaction contact time at 0.17 second. The
flowrate is 2661 SCCM.

[0241] The same catalyst and the kinetics are used in this example. The
characteristics of the catalyst bed are also same as those in the Case A.

[0242] The predicted catalyst bed temperature as a function of the reactor
length is shown in FIG. 21. The temperatures are sampled along the center
of the catalyst bed so that the peak of the curve represents the maximum
temperature of the catalyst bed. In this case, it is 246 C and located a
short distance from the beginning of the catalyst bed. The CO conversion
is projected at 81.9% and methane selectivity is at 17.0%. It would be
expected operationally that the operating temperature as driven by the
steam side pressure would likely be slightly reduced to 226 C to 229 C so
that the CO conversion would be less than about 76% and the corresponding
selectivity measurement would be expected to be slightly less than the
predicted 17%. Overall, the reactor is predicted to still be within
thermal control with a fin height of 0.5'' (1.25 cm). It is anticipated
that the inventive all-welded reactor could accommodate a 0.5'' (1.25 cm)
copper fin height for a Fischer Tropsch reactor. This move to an ultra
tall fin (0.25'' (0.625 cm) or greater) would not be possible to
accommodate with either a stainless steel fin for Fischer Tropsch or for
a brazed reactor. The ultra-tall fins from a brazed reactor would undergo
considerable compression and collapse during the high temperature and
high load brazing process. The use of the all welded reactor platform
enables the more advantageous tall fin and ultra-tall fin Fischer Tropsch
reactors.

Case C: Fin Height 1'' (2.5 cm)

[0243] A Fisher-Tropsch reaction is conducted in a microchannel reactor.
The reactor configuration is similar to the reactor in Case A. The only
difference is the process channel and the copper fin heights are 1.0''
(2.5 cm).

[0244] In this example, operating conditions are the same as those above,
except the feed flowrate which is scaled up according to the total
catalyst loading volume to keep the same reaction contact time at 0.17
second. The flowrate is 5321 SCCM.

[0245] The same catalyst and the kinetics are used in this example. The
characteristics of the catalyst bed are also same as those in the Case A.

[0246] The predicted catalyst bed temperature as a function of the reactor
length is shown in FIG. 22. The temperatures are sampled along the center
of the catalyst bed so that the peak of the curve represents the maximum
temperature of the catalyst bed. In this case, it is above 600 C. With
the catalyst amount is roughly 4 times of that in the FT reactor in Case
A, the total reaction heat passing through each fin rib is increased by
the same scaling factors. At this level of the reaction heat, even the
low heat transfer resistance inside the copper ribs becomes critical.
This can be seen from the significant fin temperature variation from the
center to the edge. Due to the high temperature on large part of the
catalyst bed, the CO conversion is projected above 90% and methane
selectivity is also significantly higher than the cases of shorter fin
heights. It is expected that for this type of exotherm that the FT
catalyst would quickly deactivate and that correspondingly the exotherm
would continue to move downstream in the axial location much akin to a
burning cigar. After burning out the FT catalyst, the overall conversion
would be low (less than 40% per pass for similar flow, temperature, and
pressure conditions) and the corresponding methane would be high (greater
than 10%).

[0247] The aforementioned examples assume perfect thermal contact of the
fin to the wall and perfect flow distribution on the coolant side with no
blocked or low flow coolant channels. It is expected for a real
manufactured large scale reactor with use of a particulate FT catalyst
that a robust fin height is preferably less than 1.3 cm (0.5 inch) to
accommodate manufacturing imperfections or operational imperfections due
to potential fouling on the coolant side during operation.